DDoS Botnet Aisuru Blankets US ISPs in Record DDoS

The world’s largest and most disruptive botnet is now drawing a majority of its firepower from compromised Internet-of-Things (IoT) devices hosted on U.S. Internet providers like AT&T, Comcast and Verizon, new evidence suggests. Experts say the heavy concentration of infected devices at U.S. providers is complicating efforts to limit collateral damage from the botnet’s attacks, which shattered previous records this week with a brief traffic flood that clocked in at nearly 30 trillion bits of data per second.

Since its debut more than a year ago, the Aisuru botnet has steadily outcompeted virtually all other IoT-based botnets in the wild, with recent attacks siphoning Internet bandwidth from an estimated 300,000 compromised hosts worldwide.

The hacked systems that get subsumed into the botnet are mostly consumer-grade routers, security cameras, digital video recorders and other devices operating with insecure and outdated firmware, and/or factory-default settings. Aisuru’s owners are continuously scanning the Internet for these vulnerable devices and enslaving them for use in distributed denial-of-service (DDoS) attacks that can overwhelm targeted servers with crippling amounts of junk traffic.

As Aisuru’s size has mushroomed, so has its punch. In May 2025, KrebsOnSecurity was hit with a near-record 6.35 terabits per second (Tbps) attack from Aisuru, which was then the largest assault that Google’s DDoS protection service Project Shield had ever mitigated. Days later, Aisuru shattered that record with a data blast in excess of 11 Tbps.

By late September, Aisuru was publicly flexing DDoS capabilities topping 22 Tbps. Then on October 6, its operators heaved a whopping 29.6 terabits of junk data packets each second at a targeted host. Hardly anyone noticed because it appears to have been a brief test or demonstration of Aisuru’s capabilities: The traffic flood lasted less only a few seconds and was pointed at an Internet server that was specifically designed to measure large-scale DDoS attacks.

Aisuru’s overlords aren’t just showing off. Their botnet is being blamed for a series of increasingly massive and disruptive attacks. Although recent assaults from Aisuru have targeted mostly ISPs that serve online gaming communities like Minecraft, those digital sieges often result in widespread collateral Internet disruption.

For the past several weeks, ISPs hosting some of the Internet’s top gaming destinations have been hit with a relentless volley of gargantuan attacks that experts say are well beyond the DDoS mitigation capabilities of most organizations connected to the Internet today.

Steven Ferguson is principal security engineer at Global Secure Layer (GSL), an ISP in Brisbane, Australia. GSL hosts TCPShield, which offers free or low-cost DDoS protection to more than 50,000 Minecraft servers worldwide. Ferguson told KrebsOnSecurity that on October 8, TCPShield was walloped with a blitz from Aisuru that flooded its network with more than 15 terabits of junk data per second.

Ferguson said that after the attack subsided, TCPShield was told by its upstream provider OVH that they were no longer welcome as a customer.

“This was causing serious congestion on their Miami external ports for several weeks, shown publicly via their weather map,” he said, explaining that TCPShield is now solely protected by GSL.

Traces from the recent spate of crippling Aisuru attacks on gaming servers can be still seen at the website blockgametracker.gg, which indexes the uptime and downtime of the top Minecraft hosts. In the following example from a series of data deluges on the evening of September 28, we can see an Aisuru botnet campaign briefly knocked TCPShield offline.

Paging through the same uptime graphs for other network operators listed shows almost all of them suffered brief but repeated outages around the same time. Here is the same uptime tracking for Minecraft servers on the network provider Cosmic (AS30456), and it shows multiple large dips that correspond to game server outages caused by Aisuru.

BOTNETS R US

Ferguson said he’s been tracking Aisuru for about three months, and recently he noticed the botnet’s composition shifted heavily toward infected systems at ISPs in the United States. Ferguson shared logs from an attack on October 8 that indexed traffic by the total volume sent through each network provider, and the logs showed that 11 of the top 20 traffic sources were U.S. based ISPs.

AT&T customers were by far the biggest U.S. contributors to that attack, followed by botted systems on Charter Communications, Comcast, T-Mobile and Verizon, Ferguson found. He said the volume of data packets per second coming from infected IoT hosts on these ISPs is often so high that it has started to affect the quality of service that ISPs are able to provide to adjacent (non-botted) customers.

“The impact extends beyond victim networks,” Ferguson said. “For instance we have seen 500 gigabits of traffic via Comcast’s network alone. This amount of egress leaving their network, especially being so US-East concentrated, will result in congestion towards other services or content trying to be reached while an attack is ongoing.”

Roland Dobbins is principal engineer at Netscout. Dobbins said Ferguson is spot on, noting that while most ISPs have effective mitigations in place to handle large incoming DDoS attacks, many are far less prepared to manage the inevitable service degradation caused by large numbers of their customers suddenly using some or all available bandwidth to attack others.

“The outbound and cross-bound DDoS attacks can be just as disruptive as the inbound stuff,” Dobbin said. “We’re now in a situation where ISPs are routinely seeing terabit-per-second plus outbound attacks from their networks that can cause operational problems.”

“The crying need for effective and universal outbound DDoS attack suppression is something that is really being highlighted by these recent attacks,” Dobbins continued. “A lot of network operators are learning that lesson now, and there’s going to be a period ahead where there’s some scrambling and potential disruption going on.”

KrebsOnSecurity sought comment from the ISPs named in Ferguson’s report. Charter Communications pointed to a recent blog post on protecting its network, stating that Charter actively monitors for both inbound and outbound attacks, and that it takes proactive action wherever possible.

“In addition to our own extensive network security, we also aim to reduce the risk of customer connected devices contributing to attacks through our Advanced WiFi solution that includes Security Shield, and we make Security Suite available to our Internet customers,” Charter wrote in an emailed response to questions. “With the ever-growing number of devices connecting to networks, we encourage customers to purchase trusted devices with secure development and manufacturing practices, use anti-virus and security tools on their connected devices, and regularly download security patches.”

A spokesperson for Comcast responded, “Currently our network is not experiencing impacts and we are able to handle the traffic.”

9 YEARS OF MIRAI

Aisuru is built on the bones of malicious code that was leaked in 2016 by the original creators of the Mirai IoT botnet. Like Aisuru, Mirai quickly outcompeted all other DDoS botnets in its heyday, and obliterated previous DDoS attack records with a 620 gigabit-per-second siege that sidelined this website for nearly four days in 2016.

The Mirai botmasters likewise used their crime machine to attack mostly Minecraft servers, but with the goal of forcing Minecraft server owners to purchase a DDoS protection service that they controlled. In addition, they rented out slices of the Mirai botnet to paying customers, some of whom used it to mask the sources of other types of cybercrime, such as click fraud.

Dobbins said Aisuru’s owners also appear to be renting out their botnet as a distributed proxy network that cybercriminal customers anywhere in the world can use to anonymize their malicious traffic and make it appear to be coming from regular residential users in the U.S.

“The people who operate this botnet are also selling (it as) residential proxies,” he said. “And that’s being used to reflect application layer attacks through the proxies on the bots as well.”

The Aisuru botnet harkens back to its predecessor Mirai in another intriguing way. One of its owners is using the Telegram handle “9gigsofram,” which corresponds to the nickname used by the co-owner of a Minecraft server protection service called Proxypipe that was heavily targeted in 2016 by the original Mirai botmasters.

Robert Coelho co-ran Proxypipe back then along with his business partner Erik “9gigsofram” Buckingham, and has spent the past nine years fine-tuning various DDoS mitigation companies that cater to Minecraft server operators and other gaming enthusiasts. Coelho said he has no idea why one of Aisuru’s botmasters chose Buckingham’s nickname, but added that it might say something about how long this person has been involved in the DDoS-for-hire industry.

“The Aisuru attacks on the gaming networks these past seven day have been absolutely huge, and you can see tons of providers going down multiple times a day,” Coelho said.

Coelho said the 15 Tbps attack this week against TCPShield was likely only a portion of the total attack volume hurled by Aisuru at the time, because much of it would have been shoved through networks that simply couldn’t process that volume of traffic all at once. Such outsized attacks, he said, are becoming increasingly difficult and expensive to mitigate.

“It’s definitely at the point now where you need to be spending at least a million dollars a month just to have the network capacity to be able to deal with these attacks,” he said.

RAPID SPREAD

Aisuru has long been rumored to use multiple zero-day vulnerabilities in IoT devices to aid its rapid growth over the past year. XLab, the Chinese security company that was the first to profile Aisuru’s rise in 2024, warned last month that one of the Aisuru botmasters had compromised the firmware distribution website for Totolink, a maker of low-cost routers and other networking gear.

“Multiple sources indicate the group allegedly compromised a router firmware update server in April and distributed malicious scripts to expand the botnet,” XLab wrote on September 15. “The node count is currently reported to be around 300,000.”

Aisuru’s operators received an unexpected boost to their crime machine in August when the U.S. Department Justice charged the alleged proprietor of Rapper Bot, a DDoS-for-hire botnet that competed directly with Aisuru for control over the global pool of vulnerable IoT systems.

Once Rapper Bot was dismantled, Aisuru’s curators moved quickly to commandeer vulnerable IoT devices that were suddenly set adrift by the government’s takedown, Dobbins said.

“Folks were arrested and Rapper Bot control servers were seized and that’s great, but unfortunately the botnet’s attack assets were then pieced out by the remaining botnets,” he said. “The problem is, even if those infected IoT devices are rebooted and cleaned up, they will still get re-compromised by something else generally within minutes of being plugged back in.”

BOTMASTERS AT LARGE

XLab’s September blog post cited multiple unnamed sources saying Aisuru is operated by three cybercriminals: “Snow,” who’s responsible for botnet development; “Tom,” tasked with finding new vulnerabilities; and “Forky,” responsible for botnet sales.

KrebsOnSecurity interviewed Forky in our May 2025 story about the record 6.3 Tbps attack from Aisuru. That story identified Forky as a 21-year-old man from Sao Paulo, Brazil who has been extremely active in the DDoS-for-hire scene since at least 2022. The FBI has seized Forky’s DDoS-for-hire domains several times over the years.

Like the original Mirai botmasters, Forky also operates a DDoS mitigation service called Botshield. Forky declined to discuss the makeup of his ISP’s clientele, or to clarify whether Botshield was more of a hosting provider or a DDoS mitigation firm. However, Forky has posted on Telegram about Botshield successfully mitigating large DDoS attacks launched against other DDoS-for-hire services.

In our previous interview, Forky acknowledged being involved in the development and marketing of Aisuru, but denied participating in attacks launched by the botnet.

Reached for comment earlier this month, Forky continued to maintain his innocence, claiming that he also is still trying to figure out who the current Aisuru botnet operators are in real life (Forky said the same thing in our May interview).

But after a week of promising juicy details, Forky came up empty-handed once again. Suspecting that Forky was merely being coy, I asked him how someone so connected to the DDoS-for-hire world could still be mystified on this point, and suggested that his inability or unwillingness to blame anyone else for Aisuru would not exactly help his case.

At this, Forky verbally bristled at being pressed for more details, and abruptly terminated our interview.

“I’m not here to be threatened with ignorance because you are stressed,” Forky replied. “They’re blaming me for those new attacks. Pretty much the whole world (is) due to your blog.”

Notorious Malware, Spam Host “Prospero” Moves to Kaspersky Lab

One of the most notorious providers of abuse-friendly “bulletproof” web hosting for cybercriminals has started routing its operations through networks run by the Russian antivirus and security firm Kaspersky Lab, KrebsOnSecurity has learned.

Security experts say the Russia-based service provider Prospero OOO (the triple O is the Russian version of “LLC”) has long been a persistent source of malicious software, botnet controllers, and a torrent of phishing websites. Last year, the French security firm Intrinsec detailed Prospero’s connections to bulletproof services advertised on Russian cybercrime forums under the names Securehost and BEARHOST.

Bulletproof hosts are so named when they earn or cultivate a reputation for ignoring legal demands and abuse complaints. And BEARHOST has been cultivating its reputation since at least 2019.

“If you need a server for a botnet, for malware, brute, scan, phishing, fakes and any other tasks, please contact us,” BEARHOST’s ad on one forum advises. “We completely ignore all abuses without exception, including SPAMHAUS and other organizations.”

Intrinsec found Prospero has courted some of Russia’s nastiest cybercrime groups, hosting control servers for multiple ransomware gangs over the past two years. Intrinsec said its analysis showed Prospero frequently hosts malware operations such as SocGholish and GootLoader, which are spread primarily via fake browser updates on hacked websites and often lay the groundwork for more serious cyber intrusions — including ransomware.

BEARHOST prides itself on the ability to evade blocking by Spamhaus, an organization that many Internet service providers around the world rely on to help identify and block sources of malware and spam. Earlier this week, Spamhaus said it noticed that Prospero was suddenly connecting to the Internet by routing through networks operated by Kaspersky Lab in Moscow.

Update, March 1, 9:43 a.m. ET: In a written statement, Kaspersky said it is aware of the public claim about the company allegedly providing services to a “bulletproof” web hosting provider. Here is their full statement:

“Kaspersky denies these claims as the company does not work and has never worked with the service provider in question. The routing through networks operated by Kaspersky doesn’t by default mean provision of the company’s services, as Kaspersky’s automatic system (AS) path might appear as a technical prefix in the network of telecom providers the company works with and provides its DDoS services.”

“Kaspersky pays great attention to conducting business ethically and ensuring that its solutions are used for their original purpose of providing cybersecurity protection. The company is currently investigating the situation to inform the company whose network could have served as a transit for a “bulletproof” web hosting provider so that the former takes the necessary measures.”

Kaspersky began selling antivirus and security software in the United States in 2005, and the company’s malware researchers have earned accolades from the security community for many important discoveries over the years. But in September 2017, the Department of Homeland Security (DHS) barred U.S. federal agencies from using Kaspersky software, mandating its removal within 90 days.

Cybersecurity reporter Kim Zetter notes that DHS didn’t cite any specific justification for its ban in 2017, but media reports quoting anonymous government officials referenced two incidents. Zetter wrote:

According to one story, an NSA contractor developing offensive hacking tools for the spy agency had Kaspersky software installed on his home computer where he was developing the tools, and the software detected the source code as malicious code and extracted it from his computer, as antivirus software is designed to do. A second story claimed that Israeli spies caught Russian government hackers using Kaspersky software to search customer systems for files containing U.S. secrets.

Kaspersky denied that anyone used its software to search for secret information on customer machines and said that the tools on the NSA worker’s machine were detected in the same way that all antivirus software detects files it deems suspicious and then quarantines or extracts them for analysis. Once Kaspersky discovered that the code its antivirus software detected on the NSA worker’s machine were not malicious programs but source code in development by the U.S. government for its hacking operations, CEO Eugene Kaspersky says he ordered workers to delete the code.

Last year, the U.S. Commerce Department banned the sale of Kaspersky software in the U.S. effective July 20, 2024. U.S. officials argued the ban was needed because Russian law requires domestic companies to cooperate in all official investigations, and thus the Russian government could force Kaspersky to secretly gather intelligence on its behalf.

Phishing data gathered last year by the Interisle Consulting Group ranked hosting networks by their size and concentration of spambot hosts, and found Prospero had a higher spam score than any other provider by far.

It remains unclear why Kaspersky is providing transit to Prospero. Doug Madory, director of Internet analysis at Kentik, said routing records show the relationship between Prospero and Kaspersky started at the beginning of December 2024.

Madory said Kaspersky’s network appears to be hosting several financial institutions, including Russia’s largest — Alfa-Bank. Kaspersky sells services to help protect customers from distributed denial-of-service (DDoS) attacks, and Madory said it could be that Prospero is simply purchasing that protection from Kaspersky.

But if that is the case, it doesn’t make the situation any better, said Zach Edwards, a senior threat researcher at the security firm Silent Push.

“In some ways, providing DDoS protection to a well-known bulletproof hosting provider may be even worse than just allowing them to connect to the rest of the Internet over your infrastructure,” Edwards said.

Experts Flag Security, Privacy Risks in DeepSeek AI App

New mobile apps from the Chinese artificial intelligence (AI) company DeepSeek have remained among the top three “free” downloads for Apple and Google devices since their debut on Jan. 25, 2025. But experts caution that many of DeepSeek’s design choices — such as using hard-coded encryption keys, and sending unencrypted user and device data to Chinese companies — introduce a number of glaring security and privacy risks.

Public interest in the DeepSeek AI chat apps swelled following widespread media reports that the upstart Chinese AI firm had managed to match the abilities of cutting-edge chatbots while using a fraction of the specialized computer chips that leading AI companies rely on. As of this writing, DeepSeek is the third most-downloaded “free” app on the Apple store, and #1 on Google Play.

DeepSeek’s rapid rise caught the attention of the mobile security firm NowSecure, a Chicago-based company that helps clients screen mobile apps for security and privacy threats. In a teardown of the DeepSeek app published today, NowSecure urged organizations to remove the DeepSeek iOS mobile app from their environments, citing security concerns.

NowSecure founder Andrew Hoog said they haven’t yet concluded an in-depth analysis of the DeepSeek app for Android devices, but that there is little reason to believe its basic design would be functionally much different.

Hoog told KrebsOnSecurity there were a number of qualities about the DeepSeek iOS app that suggest the presence of deep-seated security and privacy risks. For starters, he said, the app collects an awful lot of data about the user’s device.

“They are doing some very interesting things that are on the edge of advanced device fingerprinting,” Hoog said, noting that one property of the app tracks the device’s name — which for many iOS devices defaults to the customer’s name followed by the type of iOS device.

The device information shared, combined with the user’s Internet address and data gathered from mobile advertising companies, could be used to deanonymize users of the DeepSeek iOS app, NowSecure warned. The report notes that DeepSeek communicates with Volcengine, a cloud platform developed by ByteDance (the makers of TikTok), although NowSecure said it wasn’t clear if the data is just leveraging ByteDance’s digital transformation cloud service or if the declared information share extends further between the two companies.

Perhaps more concerning, NowSecure said the iOS app transmits device information “in the clear,” without any encryption to encapsulate the data. This means the data being handled by the app could be intercepted, read, and even modified by anyone who has access to any of the networks that carry the app’s traffic.

“The DeepSeek iOS app globally disables App Transport Security (ATS) which is an iOS platform level protection that prevents sensitive data from being sent over unencrypted channels,” the report observed. “Since this protection is disabled, the app can (and does) send unencrypted data over the internet.”

Hoog said the app does selectively encrypt portions of the responses coming from DeepSeek servers. But they also found it uses an insecure and now deprecated encryption algorithm called 3DES (aka Triple DES), and that the developers had hard-coded the encryption key. That means the cryptographic key needed to decipher those data fields can be extracted from the app itself.

There were other, less alarming security and privacy issues highlighted in the report, but Hoog said he’s confident there are additional, unseen security concerns lurking within the app’s code.

“When we see people exhibit really simplistic coding errors, as you dig deeper there are usually a lot more issues,” Hoog said. “There is virtually no priority around security or privacy. Whether cultural, or mandated by China, or a witting choice, taken together they point to significant lapse in security and privacy controls, and that puts companies at risk.”

Apparently, plenty of others share this view. Axios reported on January 30 that U.S. congressional offices are being warned not to use the app.

“[T]hreat actors are already exploiting DeepSeek to deliver malicious software and infect devices,” read the notice from the chief administrative officer for the House of Representatives. “To mitigate these risks, the House has taken security measures to restrict DeepSeek’s functionality on all House-issued devices.”

TechCrunch reports that Italy and Taiwan have already moved to ban DeepSeek over security concerns. Bloomberg writes that The Pentagon has blocked access to DeepSeek. CNBC says NASA also banned employees from using the service, as did the U.S. Navy.

Beyond security concerns tied to the DeepSeek iOS app, there are indications the Chinese AI company may be playing fast and loose with the data that it collects from and about users. On January 29, researchers at Wiz said they discovered a publicly accessible database linked to DeepSeek that exposed “a significant volume of chat history, backend data and sensitive information, including log streams, API secrets, and operational details.”

“More critically, the exposure allowed for full database control and potential privilege escalation within the DeepSeek environment, without any authentication or defense mechanism to the outside world,” Wiz wrote. [Full disclosure: Wiz is currently an advertiser on this website.]

KrebsOnSecurity sought comment on the report from DeepSeek and from Apple. This story will be updated with any substantive replies.

Booking.com Phishers May Leave You With Reservations

A number of cybercriminal innovations are making it easier for scammers to cash in on your upcoming travel plans. This story examines a recent spear-phishing campaign that ensued when a California hotel had its booking.com credentials stolen. We’ll also explore an array of cybercrime services aimed at phishers who target hotels that rely on the world’s most visited travel website.

According to the market share website statista.com, booking.com is by far the Internet’s busiest travel service, with nearly 550 million visits in September. KrebsOnSecurity last week heard from a reader whose close friend received a targeted phishing message within the Booking mobile app just minutes after making a reservation at a California hotel.

The missive bore the name of the hotel and referenced details from their reservation, claiming that booking.com’s anti-fraud system required additional information about the customer before the reservation could be finalized.

In an email to KrebsOnSecurity, booking.com confirmed one of its partners had suffered a security incident that allowed unauthorized access to customer booking information.

“Our security teams are currently investigating the incident you mentioned and can confirm that it was indeed a phishing attack targeting one of our accommodation partners, which unfortunately is not a new situation and quite common across industries,” booking.com replied. “Importantly, we want to clarify that there has been no compromise of Booking.com’s internal systems.”

Booking.com said it now requires 2FA, which forces partners to provide a one-time passcode from a mobile authentication app (Pulse) in addition to a username and password.

“2FA is required and enforced, including for partners to access payment details from customers securely,” a booking.com spokesperson wrote. “That’s why the cybercriminals follow-up with messages to try and get customers to make payments outside of our platform.”

“That said, the phishing attacks stem from partners’ machines being compromised with malware, which has enabled them to also gain access to the partners’ accounts and to send the messages that your reader has flagged,” they continued.

It’s unclear, however, if the company’s 2FA requirement is enforced for all or just newer partners. Booking.com did not respond to questions about that, and its current account security advice urges customers to enable 2FA.

In November 2023, the security firm SecureWorks detailed how scammers targeted booking.com hospitality partners with data-stealing malware. SecureWorks said these attacks had been going on since at least March 2023.

“The hotel did not enable multi-factor authentication (MFA) on its Booking.com access, so logging into the account with the stolen credentials was easy,” SecureWorks said of the booking.com partner it investigated.

In June 2024, booking.com told the BBC that phishing attacks targeting travelers had increased 900 percent, and that thieves taking advantage of new artificial intelligence (AI) tools were the primary driver of this trend.

Booking.com told the BCC the company had started using AI to fight AI-based phishing attacks. Booking.com’s statement said their investments in that arena “blocked 85 million fraudulent reservations over more than 1.5 million phishing attempts in 2023.”

The domain name in the phony booking.com website sent to our reader’s friend — guestssecureverification[.]com — was registered to the email address ilotirabec207@gmail.com. According to DomainTools.com, this email address was used to register more than 700 other phishing domains in the past month alone.

Many of the 700+ domains appear to target hospitality companies, including platforms like booking.com and Airbnb. Others seem crafted to phish users of Shopify, Steam, and a variety of financial platforms. A full, defanged list of domains is available here.

A cursory review of recent posts across dozens of cybercrime forums monitored by the security firm Intel 471 shows there is a great demand for compromised booking.com accounts belonging to hotels and other partners.

One post last month on the Russian-language hacking forum BHF offered up to $5,000 for each hotel account. This seller claims to help people monetize hacked booking.com partners, apparently by using the stolen credentials to set up fraudulent listings.

A service advertised on the English-language crime community BreachForums in October courts phishers who may need help with certain aspects of their phishing campaigns targeting booking.com partners. Those include more than two million hotel email addresses, and services designed to help phishers organize large volumes of phished records. Customers can interact with the service via an automated Telegram bot.

Some cybercriminals appear to have used compromised booking.com accounts to power their own travel agencies catering to fellow scammers, with up to 50 percent discounts on hotel reservations through booking.com. Others are selling ready-to-use “config” files designed to make it simple to conduct automated login attempts against booking.com administrator accounts.

SecureWorks found the phishers targeting booking.com partner hotels used malware to steal credentials. But today’s thieves can just as easily just visit crime bazaars online and purchase stolen credentials to cloud services that do not enforce 2FA for all accounts.

That is exactly what transpired over the past year with many customers of the cloud data storage giant Snowflake. In late 2023, cybercriminals figured out that while tons of companies had stashed enormous amounts of customer data at Snowflake, many of those customer accounts were not protected by 2FA.

Snowflake responded by making 2FA mandatory for all new customers. But that change came only after thieves used stolen credentials to siphon data from 160 companies — including AT&T, Lending Tree and TicketMaster.

The Stark Truth Behind the Resurgence of Russia’s Fin7

The Russia-based cybercrime group dubbed “Fin7,” known for phishing and malware attacks that have cost victim organizations an estimated $3 billion in losses since 2013, was declared dead last year by U.S. authorities. But experts say Fin7 has roared back to life in 2024 — setting up thousands of websites mimicking a range of media and technology companies — with the help of Stark Industries Solutions, a sprawling hosting provider that is a persistent source of cyberattacks against enemies of Russia.

In May 2023, the U.S. attorney for Washington state declared “Fin7 is an entity no more,” after prosecutors secured convictions and prison sentences against three men found to be high-level Fin7 hackers or managers. This was a bold declaration against a group that the U.S. Department of Justice described as a criminal enterprise with more than 70 people organized into distinct business units and teams.

The first signs of Fin7’s revival came in April 2024, when Blackberry wrote about an intrusion at a large automotive firm that began with malware served by a typosquatting attack targeting people searching for a popular free network scanning tool.

Now, researchers at security firm Silent Push say they have devised a way to map out Fin7’s rapidly regrowing cybercrime infrastructure, which includes more than 4,000 hosts that employ a range of exploits, from typosquatting and booby-trapped ads to malicious browser extensions and spearphishing domains.

Silent Push said it found Fin7 domains targeting or spoofing brands including American Express, Affinity Energy, Airtable, Alliant, Android Developer, Asana, Bitwarden, Bloomberg, Cisco (Webex), CNN, Costco, Dropbox, Grammarly, Google, Goto.com, Harvard, Lexis Nexis, Meta, Microsoft 365, Midjourney, Netflix, Paycor, Quickbooks, Quicken, Reuters, Regions Bank Onepass, RuPay, SAP (Ariba), Trezor, Twitter/X, Wall Street Journal, Westlaw, and Zoom, among others.

Zach Edwards, senior threat analyst at Silent Push, said many of the Fin7 domains are innocuous-looking websites for generic businesses that sometimes include text from default website templates (the content on these sites often has nothing to do with the entity’s stated business or mission).

Edwards said Fin7 does this to “age” the domains and to give them a positive or at least benign reputation before they’re eventually converted for use in hosting brand-specific phishing pages.

“It took them six to nine months to ramp up, but ever since January of this year they have been humming, building a giant phishing infrastructure and aging domains,” Edwards said of the cybercrime group.

In typosquatting attacks, Fin7 registers domains that are similar to those for popular free software tools. Those look-alike domains are then advertised on Google so that sponsored links to them show up prominently in search results, which is usually above the legitimate source of the software in question.

According to Silent Push, the software currently being targeted by Fin7 includes 7-zip, PuTTY, ProtectedPDFViewer, AIMP, Notepad++, Advanced IP Scanner, AnyDesk, pgAdmin, AutoDesk, Bitwarden, Rest Proxy, Python, Sublime Text, and Node.js.

In May 2024, security firm eSentire warned that Fin7 was spotted using sponsored Google ads to serve pop-ups prompting people to download phony browser extensions that install malware. Malwarebytes blogged about a similar campaign in April, but did not attribute the activity to any particular group.

Edwards said Silent Push discovered the new Fin7 domains after a hearing from an organization that was targeted by Fin7 in years past and suspected the group was once again active. Searching for hosts that matched Fin7’s known profile revealed just one active site. But Edwards said that one site pointed to many other Fin7 properties at Stark Industries Solutions, a large hosting provider that materialized just two weeks before Russia invaded Ukraine.

As KrebsOnSecurity wrote in May, Stark Industries Solutions is being used as a staging ground for wave after wave of cyberattacks against Ukraine that have been tied to Russian military and intelligence agencies.

“FIN7 rents a large amount of dedicated IP on Stark Industries,” Edwards said. “Our analysts have discovered numerous Stark Industries IPs that are solely dedicated to hosting FIN7 infrastructure.”

Fin7 once famously operated behind fake cybersecurity companies — with names like Combi Security and Bastion Secure — which they used for hiring security experts to aid in ransomware attacks. One of the new Fin7 domains identified by Silent Push is cybercloudsec[.]com, which promises to “grow your business with our IT, cyber security and cloud solutions.”

Like other phishing groups, Fin7 seizes on current events, and at the moment it is targeting tourists visiting France for the Summer Olympics later this month. Among the new Fin7 domains Silent Push found are several sites phishing people seeking tickets at the Louvre.

“We believe this research makes it clear that Fin7 is back and scaling up quickly,” Edwards said. “It’s our hope that the law enforcement community takes notice of this and puts Fin7 back on their radar for additional enforcement actions, and that quite a few of our competitors will be able to take this pool and expand into all or a good chunk of their infrastructure.”

Further reading:

Stark Industries Solutions: An Iron Hammer in the Cloud.

A 2022 deep dive on Fin7 from the Swiss threat intelligence firm Prodaft (PDF).

April’s Patch Tuesday Brings Record Number of Fixes

If only Patch Tuesdays came around infrequently — like total solar eclipse rare — instead of just creeping up on us each month like The Man in the Moon. Although to be fair, it would be tough for Microsoft to eclipse the number of vulnerabilities fixed in this month’s patch batch — a record 147 flaws in Windows and related software.

Yes, you read that right. Microsoft today released updates to address 147 security holes in Windows, Office, Azure, .NET Framework, Visual Studio, SQL Server, DNS Server, Windows Defender, Bitlocker, and Windows Secure Boot.

“This is the largest release from Microsoft this year and the largest since at least 2017,” said Dustin Childs, from Trend Micro’s Zero Day Initiative (ZDI). “As far as I can tell, it’s the largest Patch Tuesday release from Microsoft of all time.”

Tempering the sheer volume of this month’s patches is the middling severity of many of the bugs. Only three of April’s vulnerabilities earned Microsoft’s most-dire “critical” rating, meaning they can be abused by malware or malcontents to take remote control over unpatched systems with no help from users.

Most of the flaws that Microsoft deems “more likely to be exploited” this month are marked as “important,” which usually involve bugs that require a bit more user interaction (social engineering) but which nevertheless can result in system security bypass, compromise, and the theft of critical assets.

Ben McCarthy, lead cyber security engineer at Immersive Labs called attention to CVE-2024-20670, an Outlook for Windows spoofing vulnerability described as being easy to exploit. It involves convincing a user to click on a malicious link in an email, which can then steal the user’s password hash and authenticate as the user in another Microsoft service.

Another interesting bug McCarthy pointed to is CVE-2024-29063, which involves hard-coded credentials in Azure’s search backend infrastructure that could be gleaned by taking advantage of Azure AI search.

“This along with many other AI attacks in recent news shows a potential new attack surface that we are just learning how to mitigate against,” McCarthy said. “Microsoft has updated their backend and notified any customers who have been affected by the credential leakage.”

CVE-2024-29988 is a weakness that allows attackers to bypass Windows SmartScreen, a technology Microsoft designed to provide additional protections for end users against phishing and malware attacks. Childs said one of ZDI’s researchers found this vulnerability being exploited in the wild, although Microsoft doesn’t currently list CVE-2024-29988 as being exploited.

“I would treat this as in the wild until Microsoft clarifies,” Childs said. “The bug itself acts much like CVE-2024-21412 – a [zero-day threat from February] that bypassed the Mark of the Web feature and allows malware to execute on a target system. Threat actors are sending exploits in a zipped file to evade EDR/NDR detection and then using this bug (and others) to bypass Mark of the Web.”

Update, 7:46 p.m. ET: A previous version of this story said there were no zero-day vulnerabilities fixed this month. BleepingComputer reports that Microsoft has since confirmed that there are actually two zero-days. One is the flaw Childs just mentioned (CVE-2024-21412), and the other is CVE-2024-26234, described as a “proxy driver spoofing” weakness.

Satnam Narang at Tenable notes that this month’s release includes fixes for two dozen flaws in Windows Secure Boot, the majority of which are considered “Exploitation Less Likely” according to Microsoft.

“However, the last time Microsoft patched a flaw in Windows Secure Boot in May 2023 had a notable impact as it was exploited in the wild and linked to the BlackLotus UEFI bootkit, which was sold on dark web forums for $5,000,” Narang said. “BlackLotus can bypass functionality called secure boot, which is designed to block malware from being able to load when booting up. While none of these Secure Boot vulnerabilities addressed this month were exploited in the wild, they serve as a reminder that flaws in Secure Boot persist, and we could see more malicious activity related to Secure Boot in the future.”

For links to individual security advisories indexed by severity, check out ZDI’s blog and the Patch Tuesday post from the SANS Internet Storm Center. Please consider backing up your data or your drive before updating, and drop a note in the comments here if you experience any issues applying these fixes.

Adobe today released nine patches tackling at least two dozen vulnerabilities in a range of software products, including Adobe After Effects, Photoshop, Commerce, InDesign, Experience Manager, Media Encoder, Bridge, Illustrator, and Adobe Animate.

KrebsOnSecurity needs to correct the record on a point mentioned at the end of March’s “Fat Patch Tuesday” post, which looked at new AI capabilities built into Adobe Acrobat that are turned on by default. Adobe has since clarified that its apps won’t use AI to auto-scan your documents, as the original language in its FAQ suggested.

“In practice, no document scanning or analysis occurs unless a user actively engages with the AI features by agreeing to the terms, opening a document, and selecting the AI Assistant or generative summary buttons for that specific document,” Adobe said earlier this month.

U.S. Internet Leaked Years of Internal, Customer Emails

The Minnesota-based Internet provider U.S. Internet Corp. has a business unit called Securence, which specializes in providing filtered, secure email services to businesses, educational institutions and government agencies worldwide. But until it was notified last week, U.S. Internet was publishing more than a decade’s worth of its internal email — and that of thousands of Securence clients — in plain text out on the Internet and just a click away for anyone with a Web browser.

Headquartered in Minnetonka, Minn., U.S. Internet is a regional ISP that provides fiber and wireless Internet service. The ISP’s Securence division bills itself “a leading provider of email filtering and management software that includes email protection and security services for small business, enterprise, educational and government institutions worldwide.”

Roughly a week ago, KrebsOnSecurity was contacted by Hold Security, a Milwaukee-based cybersecurity firm. Hold Security founder Alex Holden said his researchers had unearthed a public link to a U.S. Internet email server listing more than 6,500 domain names, each with its own clickable link.

Drilling down into those individual domain links revealed inboxes for each employee or user of these exposed host names. Some of the emails dated back to 2008; others were as recent as the present day.

Securence counts among its customers dozens of state and local governments, including: nc.gov — the official website of North Carolina; stillwatermn.gov, the website for the city of Stillwater, Minn.; and cityoffrederickmd.gov, the website for the government of Frederick, Md.

Incredibly, included in this giant index of U.S. Internet customer emails were the internal messages for every current and former employee of U.S. Internet and its subsidiary USI Wireless. Since that index also included the messages of U.S. Internet’s CEO Travis Carter, KrebsOnSecurity forwarded one of Mr. Carter’s own recent emails to him, along with a request to understand how exactly the company managed to screw things up so spectacularly.

Within minutes of that notification, U.S. Internet pulled all of the published inboxes offline. Mr. Carter responded and said his team was investigating how it happened. In the same breath, the CEO asked if KrebsOnSecurity does security consulting for hire (I do not).

[Author’s note: Perhaps Mr. Carter was frantically casting about for any expertise he could find in a tough moment. But I found the request personally offensive, because I couldn’t shake the notion that maybe the company was hoping it could buy my silence.]

Earlier this week, Mr. Carter replied with a highly technical explanation that ultimately did little to explain why or how so many internal and customer inboxes were published in plain text on the Internet.

“The feedback from my team was a issue with the Ansible playbook that controls the Nginx configuration for our IMAP servers,” Carter said, noting that this incorrect configuration was put in place by a former employee and never caught. U.S. Internet has not shared how long these messages were exposed.

“The rest of the platform and other backend services are being audited to verify the Ansible playbooks are correct,” Carter said.

Holden said he also discovered that hackers have been abusing a Securence link scrubbing and anti-spam service called Url-Shield to create links that look benign but instead redirect visitors to hacked and malicious websites.

“The bad guys modify the malicious link reporting into redirects to their own malicious sites,” Holden said. “That’s how the bad guys drive traffic to their sites and increase search engine rankings.”

For example, clicking the Securence link shown in the screenshot directly above leads one to a website that tries to trick visitors into allowing site notifications by couching the request as a CAPTCHA request designed to separate humans from bots. After approving the deceptive CAPTCHA/notification request, the link forwards the visitor to a Russian internationalized domain name (рпроаг[.]рф).

U.S. Internet has not responded to questions about how long it has been exposing all of its internal and customer emails, or when the errant configuration changes were made. The company also still has not disclosed the incident on its website. The last press release on the site dates back to March 2020.

KrebsOnSecurity has been writing about data breaches for nearly two decades, but this one easily takes the cake in terms of the level of incompetence needed to make such a huge mistake unnoticed. I’m not sure what the proper response from authorities or regulators should be to this incident, but it’s clear that U.S. Internet should not be allowed to manage anyone’s email unless and until it can demonstrate more transparency, and prove that it has radically revamped its security.

Alleged Extortioner of Psychotherapy Patients Faces Trial

Prosecutors in Finland this week commenced their criminal trial against Julius Kivimäki, a 26-year-old Finnish man charged with extorting a once popular and now-bankrupt online psychotherapy practice and thousands of its patients. In a 2,200-page report, Finnish authorities laid out how they connected the extortion spree to Kivimäki, a notorious hacker who was convicted in 2015 of perpetrating tens of thousands of cybercrimes, including data breaches, payment fraud, operating a botnet and calling in bomb threats.

In November 2022, Kivimäki was charged with attempting to extort money from the Vastaamo Psychotherapy Center. In that breach, which occurred in October 2020, a hacker using the handle “Ransom Man” threatened to publish patient psychotherapy notes if Vastaamo did not pay a six-figure ransom demand.

Vastaamo refused, so Ransom Man shifted to extorting individual patients — sending them targeted emails threatening to publish their therapy notes unless paid a 500-euro ransom. When Ransom Man found little success extorting patients directly, they uploaded to the dark web a large compressed file containing all of the stolen Vastaamo patient records.

Security experts soon discovered Ransom Man had mistakenly included an entire copy of their home folder, where investigators found many clues pointing to Kivimäki’s involvement. By that time, Kivimäki was no longer in Finland, but the Finnish government nevertheless charged Kivimäki in absentia with the Vastaamo hack. The 2,200-page evidence document against Kivimäki suggests he enjoyed a lavish lifestyle while on the lam, frequenting luxury resorts and renting fabulously expensive cars and living quarters.

But in February 2023, Kivimäki was arrested in France after authorities there responded to a domestic disturbance call and found the defendant sleeping off a hangover on the couch of a woman he’d met the night before. The French police grew suspicious when the 6′ 3″ blonde, green-eyed man presented an ID that stated he was of Romanian nationality.

Finnish prosecutors showed that Kivimäki’s credit card had been used to pay for the virtual server that hosted the stolen Vastaamo patient notes. What’s more, the home folder included in the Vastaamo patient data archive also allowed investigators to peer into other cybercrime projects of the accused, including domains that Ransom Man had access to as well as a lengthy history of commands he’d executed on the rented virtual server.

Some of those domains allegedly administered by Kivimäki were set up to smear the reputations of different companies and individuals. One of those was a website that claimed to have been authored by a person who headed up IT infrastructure for a major bank in Norway which discussed the idea of legalizing child sexual abuse.

Another domain hosted a fake blog that besmirched the reputation of a Tulsa, Okla. man whose name was attached to blog posts about supporting the “white pride” movement and calling for a pardon of the Oklahoma City bomber Timothy McVeigh.

Kivimäki appears to have sought to sully the name of this reporter as well. The 2,200-page document shows that Kivimäki owned and operated the domain krebsonsecurity[.]org, which hosted various hacking tools that Kivimäki allegedly used, including programs for mass-scanning the Internet for systems vulnerable to known security flaws, as well as scripts for cracking database server usernames and passwords, and downloading databases.

Mikko Hyppönen, chief research officer at WithSecure (formerly F-Secure), said the Finnish authorities have done “amazing work,” and that “it’s rare to have this much evidence for a cybercrime case.”

Petteri Järvinen is a respected IT expert and author who has been following the trial, and he said the prosecution’s case so far has been strong.

“The National Bureau of Investigation has done a good job and Mr Kivimäki for his part some elementary mistakes,” Järvinen wrote on LinkedIn. “This sends an important message: online crime does not pay. Traces are left in the digital world too, even if it is very tedious for the police to collect them from servers all around the world.”

Antti Kurittu is an information security specialist and a former criminal investigator. In 2013, Kurittu worked on an investigation involving Kivimäki’s use of the Zbot botnet, among other activities Kivimäki engaged in as a member of the hacker group Hack the Planet (HTP). Kurittu said it remains to be seen if the prosecution can make their case, and if the defense has any answers to all of the evidence presented.

“Based on the public pretrial investigation report, it looks like the case has a lot of details that seem very improbable to be coincidental,” Kurittu told KrebsOnSecurity. “For example, a full copy of the Vastaamo patient database was found on a server that belonged to Scanifi, a company with no reasonable business that Kivimäki was affiliated with. The leaked home folder contents were also connected to Kivimäki and were found on servers that were under his control.”

The Finnish daily yle.fi reports that Kivimäki’s lawyers sought to have their client released from confinement for the remainder of his trial, noting that the defendant has already been detained for eight months.

The court denied that request, saying the defendant was still a flight risk. Kivimäki’s trial is expected to continue until February 2024, in part to accommodate testimony from a large number of victims. Prosecutors are seeking a seven-year sentence for Kivimäki.