KrebsOnSecurity Hit With Near-Record 6.3 Tbps DDoS

KrebsOnSecurity last week was hit by a near record distributed denial-of-service (DDoS) attack that clocked in at more than 6.3 terabits of data per second (a terabit is one trillion bits of data). The brief attack appears to have been a test run for a massive new Internet of Things (IoT) botnet capable of launching crippling digital assaults that few web destinations can withstand. Read on for more about the botnet, the attack, and the apparent creator of this global menace.

For reference, the 6.3 Tbps attack last week was ten times the size of the assault launched against this site in 2016 by the Mirai IoT botnet, which held KrebsOnSecurity offline for nearly four days. The 2016 assault was so large that Akamai – which was providing pro-bono DDoS protection for KrebsOnSecurity at the time — asked me to leave their service because the attack was causing problems for their paying customers.

Since the Mirai attack, KrebsOnSecurity.com has been behind the protection of Project Shield, a free DDoS defense service that Google provides to websites offering news, human rights, and election-related content. Google Security Engineer Damian Menscher told KrebsOnSecurity the May 12 attack was the largest Google has ever handled. In terms of sheer size, it is second only to a very similar attack that Cloudflare mitigated and wrote about in April.

After comparing notes with Cloudflare, Menscher said the botnet that launched both attacks bears the fingerprints of Aisuru, a digital siege machine that first surfaced less than a year ago. Menscher said the attack on KrebsOnSecurity lasted less than a minute, hurling large UDP data packets at random ports at a rate of approximately 585 million data packets per second.

“It was the type of attack normally designed to overwhelm network links,” Menscher said, referring to the throughput connections between and among various Internet service providers (ISPs). “For most companies, this size of attack would kill them.”

The Aisuru botnet comprises a globally-dispersed collection of hacked IoT devices, including routers, digital video recorders and other systems that are commandeered via default passwords or software vulnerabilities. As documented by researchers at QiAnXin XLab, the botnet was first identified in an August 2024 attack on a large gaming platform.

Aisuru reportedly went quiet after that exposure, only to reappear in November with even more firepower and software exploits. In a January 2025 report, XLab found the new and improved Aisuru (a.k.a. “Airashi“) had incorporated a previously unknown zero-day vulnerability in Cambium Networks cnPilot routers.

NOT FORKING AROUND

The people behind the Aisuru botnet have been peddling access to their DDoS machine in public Telegram chat channels that are closely monitored by multiple security firms. In August 2024, the botnet was rented out in subscription tiers ranging from $150 per day to $600 per week, offering attacks of up to two terabits per second.

“You may not attack any measurement walls, healthcare facilities, schools or government sites,” read a notice posted on Telegram by the Aisuru botnet owners in August 2024.

Interested parties were told to contact the Telegram handle “@yfork” to purchase a subscription. The account @yfork previously used the nickname “Forky,” an identity that has been posting to public DDoS-focused Telegram channels since 2021.

According to the FBI, Forky’s DDoS-for-hire domains have been seized in multiple law enforcement operations over the years. Last year, Forky said on Telegram he was selling the domain stresser[.]best, which saw its servers seized by the FBI in 2022 as part of an ongoing international law enforcement effort aimed at diminishing the supply of and demand for DDoS-for-hire services.

“The operator of this service, who calls himself ‘Forky,’ operates a Telegram channel to advertise features and communicate with current and prospective DDoS customers,” reads an FBI seizure warrant (PDF) issued for stresser[.]best. The FBI warrant stated that on the same day the seizures were announced, Forky posted a link to a story on this blog that detailed the domain seizure operation, adding the comment, “We are buying our new domains right now.”

Approximately ten hours later, Forky posted again, including a screenshot of the stresser[.]best user dashboard, instructing customers to use their saved passwords for the old website on the new one.

A review of Forky’s posts to public Telegram channels — as indexed by the cyber intelligence firms Unit 221B and Flashpoint — reveals a 21-year-old individual who claims to reside in Brazil [full disclosure: Flashpoint is currently an advertiser on this blog].

Since late 2022, Forky’s posts have frequently promoted a DDoS mitigation company and ISP that he operates called botshield[.]io. The Botshield website is connected to a business entity registered in the United Kingdom called Botshield LTD, which lists a 21-year-old woman from Sao Paulo, Brazil as the director. Internet routing records indicate Botshield (AS213613) currently controls several hundred Internet addresses that were allocated to the company earlier this year.

Domaintools.com reports that botshield[.]io was registered in July 2022 to a Kaike Southier Leite in Sao Paulo. A LinkedIn profile by the same name says this individual is a network specialist from Brazil who works in “the planning and implementation of robust network infrastructures, with a focus on security, DDoS mitigation, colocation and cloud server services.”

MEET FORKY

In his posts to public Telegram chat channels, Forky has hardly attempted to conceal his whereabouts or identity. In countless chat conversations indexed by Unit 221B, Forky could be seen talking about everyday life in Brazil, often remarking on the extremely low or high prices in Brazil for a range of goods, from computer and networking gear to narcotics and food.

Reached via Telegram, Forky claimed he was “not involved in this type of illegal actions for years now,” and that the project had been taken over by other unspecified developers. Forky initially told KrebsOnSecurity he had been out of the botnet scene for years, only to concede this wasn’t true when presented with public posts on Telegram from late last year that clearly showed otherwise.

Forky denied being involved in the attack on KrebsOnSecurity, but acknowledged that he helped to develop and market the Aisuru botnet. Forky claims he is now merely a staff member for the Aisuru botnet team, and that he stopped running the botnet roughly two months ago after starting a family. Forky also said the woman named as director of Botshield is related to him.

Forky offered equivocal, evasive responses to a number of questions about the Aisuru botnet and his business endeavors. But on one point he was crystal clear:

“I have zero fear about you, the FBI, or Interpol,” Forky said, asserting that he is now almost entirely focused on their hosting business — 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.

DomainTools finds the same Sao Paulo street address in the registration records for botshield[.]io was used to register several other domains, including cant-mitigate[.]us. The email address in the WHOIS records for that domain is forkcontato@gmail.com, which DomainTools says was used to register the domain for the now-defunct DDoS-for-hire service stresser[.]us, one of the domains seized in the FBI’s 2023 crackdown.

On May 8, 2023, the U.S. Department of Justice announced the seizure of stresser[.]us, along with a dozen other domains offering DDoS services. The DOJ said ten of the 13 domains were reincarnations of services that were seized during a prior sweep in December, which targeted 48 top stresser services (also known as “booters”).

Forky claimed he could find out who attacked my site with Aisuru. But when pressed a day later on the question, Forky said he’d come up empty-handed.

“I tried to ask around, all the big guys are not retarded enough to attack you,” Forky explained in an interview on Telegram. “I didn’t have anything to do with it. But you are welcome to write the story and try to put the blame on me.”

THE GHOST OF MIRAI

The 6.3 Tbps attack last week caused no visible disruption to this site, in part because it was so brief — lasting approximately 45 seconds. DDoS attacks of such magnitude and brevity typically are produced when botnet operators wish to test or demonstrate their firepower for the benefit of potential buyers. Indeed, Google’s Menscher said it is likely that both the May 12 attack and the slightly larger 6.5 Tbps attack against Cloudflare last month were simply tests of the same botnet’s capabilities.

In many ways, the threat posed by the Aisuru/Airashi botnet is reminiscent of Mirai, an innovative IoT malware strain that emerged in the summer of 2016 and successfully out-competed virtually all other IoT malware strains in existence at the time.

As first revealed by KrebsOnSecurity in January 2017, the Mirai authors were two U.S. men who co-ran a DDoS mitigation service — even as they were selling far more lucrative DDoS-for-hire services using the most powerful botnet on the planet.

Less than a week after the Mirai botnet was used in a days-long DDoS against KrebsOnSecurity, the Mirai authors published the source code to their botnet so that they would not be the only ones in possession of it in the event of their arrest by federal investigators.

Ironically, the leaking of the Mirai source is precisely what led to the eventual unmasking and arrest of the Mirai authors, who went on to serve probation sentences that required them to consult with FBI investigators on DDoS investigations. But that leak also rapidly led to the creation of dozens of Mirai botnet clones, many of which were harnessed to fuel their own powerful DDoS-for-hire services.

Menscher told KrebsOnSecurity that as counterintuitive as it may sound, the Internet as a whole would probably be better off if the source code for Aisuru became public knowledge. After all, he said, the people behind Aisuru are in constant competition with other IoT botnet operators who are all striving to commandeer a finite number of vulnerable IoT devices globally.

Such a development would almost certainly cause a proliferation of Aisuru botnet clones, he said, but at least then the overall firepower from each individual botnet would be greatly diminished — or at least within range of the mitigation capabilities of most DDoS protection providers.

Barring a source code leak, Menscher said, it would be nice if someone published the full list of software exploits being used by the Aisuru operators to grow their botnet so quickly.

“Part of the reason Mirai was so dangerous was that it effectively took out competing botnets,” he said. “This attack somehow managed to compromise all these boxes that nobody else knows about. Ideally, we’d want to see that fragmented out, so that no [individual botnet operator] controls too much.”

New 0-Day Attacks Linked to China’s ‘Volt Typhoon’

Malicious hackers are exploiting a zero-day vulnerability in Versa Director, a software product used by many Internet and IT service providers. Researchers believe the activity is linked to Volt Typhoon, a Chinese cyber espionage group focused on infiltrating critical U.S. networks and laying the groundwork for the ability to disrupt communications between the United States and Asia during any future armed conflict with China.

Versa Director systems are primarily used by Internet service providers (ISPs), as well as managed service providers (MSPs) that cater to the IT needs of many small to mid-sized businesses simultaneously. In a security advisory published Aug. 26, Versa urged customers to deploy a patch for the vulnerability (CVE-2024-39717), which the company said is fixed in Versa Director 22.1.4 or later.

Versa said the weakness allows attackers to upload a file of their choosing to vulnerable systems. The advisory placed much of the blame on Versa customers who “failed to implement system hardening and firewall guidelines…leaving a management port exposed on the internet that provided the threat actors with initial access.”

Versa’s advisory doesn’t say how it learned of the zero-day flaw, but its vulnerability listing at mitre.org acknowledges “there are reports of others based on backbone telemetry observations of a 3rd party provider, however these are unconfirmed to date.”

Those third-party reports came in late June 2024 from Michael Horka, senior lead information security engineer at Black Lotus Labs, the security research arm of Lumen Technologies, which operates one of the global Internet’s largest backbones.

In an interview with KrebsOnSecurity, Horka said Black Lotus Labs identified a web-based backdoor on Versa Director systems belonging to four U.S. victims and one non-U.S. victim in the ISP and MSP sectors, with the earliest known exploit activity occurring at a U.S. ISP on June 12, 2024.

“This makes Versa Director a lucrative target for advanced persistent threat (APT) actors who would want to view or control network infrastructure at scale, or pivot into additional (or downstream) networks of interest,” Horka wrote in a blog post published today.

Black Lotus Labs said it assessed with “medium” confidence that Volt Typhoon was responsible for the compromises, noting the intrusions bear the hallmarks of the Chinese state-sponsored espionage group — including zero-day attacks targeting IT infrastructure providers, and Java-based backdoors that run in memory only.

In May 2023, the National Security Agency (NSA), the Federal Bureau of Investigation (FBI), and the Cybersecurity Infrastructure Security Agency (CISA) issued a joint warning (PDF) about Volt Typhoon, also known as “Bronze Silhouette” and “Insidious Taurus,” which described how the group uses small office/home office (SOHO) network devices to hide their activity.

In early December 2023, Black Lotus Labs published its findings on “KV-botnet,” thousands of compromised SOHO routers that were chained together to form a covert data transfer network supporting various Chinese state-sponsored hacking groups, including Volt Typhoon.

In January 2024, the U.S. Department of Justice disclosed the FBI had executed a court-authorized takedown of the KV-botnet shortly before Black Lotus Labs released its December report.

In February 2024, CISA again joined the FBI and NSA in warning Volt Typhoon had compromised the IT environments of multiple critical infrastructure organizations — primarily in communications, energy, transportation systems, and water and wastewater sectors — in the continental and non-continental United States and its territories, including Guam.

“Volt Typhoon’s choice of targets and pattern of behavior is not consistent with traditional cyber espionage or intelligence gathering operations, and the U.S. authoring agencies assess with high confidence that Volt Typhoon actors are pre-positioning themselves on IT networks to enable lateral movement to OT [operational technology] assets to disrupt functions,” that alert warned.

In a speech at Vanderbilt University in April, FBI Director Christopher Wray said China is developing the “ability to physically wreak havoc on our critical infrastructure at a time of its choosing,” and that China’s plan is to “land blows against civilian infrastructure to try to induce panic.”

Ryan English, an information security engineer at Lumen, said it’s disappointing his employer didn’t at least garner an honorable mention in Versa’s security advisory. But he said he’s glad there are now a lot fewer Versa systems exposed to this attack.

“Lumen has for the last nine weeks been very intimate with their leadership with the goal in mind of helping them mitigate this,” English said. “We’ve given them everything we could along the way, so it kind of sucks being referenced just as a third party.”

Who and What is Behind the Malware Proxy Service SocksEscort?

Researchers this month uncovered a two-year-old Linux-based remote access trojan dubbed AVrecon that enslaves Internet routers into botnet that bilks online advertisers and performs password-spraying attacks. Now new findings reveal that AVrecon is the malware engine behind a 12-year-old service called SocksEscort, which rents hacked residential and small business devices to cybercriminals looking to hide their true location online.

In a report released July 12, researchers at Lumen’s Black Lotus Labs called the AVrecon botnet “one of the largest botnets targeting small-office/home-office (SOHO) routers seen in recent history,” and a crime machine that has largely evaded public attention since first being spotted in mid-2021.

“The malware has been used to create residential proxy services to shroud malicious activity such as password spraying, web-traffic proxying and ad fraud,” the Lumen researchers wrote.

Malware-based anonymity networks are a major source of unwanted and malicious web traffic directed at online retailers, Internet service providers (ISPs), social networks, email providers and financial institutions. And a great many of these “proxy” networks are marketed primarily to cybercriminals seeking to anonymize their traffic by routing it through an infected PC, router or mobile device.

Proxy services can be used in a legitimate manner for several business purposes — such as price comparisons or sales intelligence — but they are massively abused for hiding cybercrime activity because they make it difficult to trace malicious traffic to its original source. Proxy services also let users appear to be getting online from nearly anywhere in the world, which is useful if you’re a cybercriminal who is trying to impersonate someone from a specific place.

Spur.us, a startup that tracks proxy services, told KrebsOnSecurity that the Internet addresses Lumen tagged as the AVrecon botnet’s “Command and Control” (C2) servers all tie back to a long-running proxy service called SocksEscort.

SocksEscort[.]com, is what’s known as a “SOCKS Proxy” service. The SOCKS (or SOCKS5) protocol allows Internet users to channel their Web traffic through a proxy server, which then passes the information on to the intended destination. From a website’s perspective, the traffic of the proxy network customer appears to originate from a rented/malware-infected PC tied to a residential ISP customer, not from the proxy service customer.

Spur tracks SocksEscort as a malware-based proxy offering, which means the machines doing the proxying of traffic for SocksEscort customers have been infected with malicious software that turns them into a traffic relay. Usually, these users have no idea their systems are compromised.

Spur says the SocksEscort proxy service requires customers to install a Windows based application in order to access a pool of more than 10,000 hacked devices worldwide.

“We created a fingerprint to identify the call-back infrastructure for SocksEscort proxies,” Spur co-founder Riley Kilmer said. “Looking at network telemetry, we were able to confirm that we saw victims talking back to it on various ports.”

According to Kilmer, AVrecon is the malware that gives SocksEscort its proxies.

“When Lumen released their report and IOCs [indicators of compromise], we queried our system for which proxy service call-back infrastructure overlapped with their IOCs,” Kilmer continued. “The second stage C2s they identified were the same as the IPs we labeled for SocksEscort.”

Lumen’s research team said the purpose of AVrecon appears to be stealing bandwidth – without impacting end-users – in order to create a residential proxy service to help launder malicious activity and avoid attracting the same level of attention from Tor-hidden services or commercially available VPN services.

“This class of cybercrime activity threat may evade detection because it is less likely than a crypto-miner to be noticed by the owner, and it is unlikely to warrant the volume of abuse complaints that internet-wide brute-forcing and DDoS-based botnets typically draw,” Lumen’s Black Lotus researchers wrote.

Preserving bandwidth for both customers and victims was a primary concern for SocksEscort in July 2022, when 911S5 — at the time the world’s largest known malware proxy network — got hacked and imploded just days after being exposed in a story here. Kilmer said after 911’s demise, SocksEscort closed its registration for several months to prevent an influx of new users from swamping the service.

Danny Adamitis, principal information security researcher at Lumen and co-author of the report on AVrecon, confirmed Kilmer’s findings, saying the C2 data matched up with what Spur was seeing for SocksEscort dating back to September 2022.

Adamitis said that on July 13 — the day after Lumen published research on AVrecon and started blocking any traffic to the malware’s control servers — the people responsible for maintaining the botnet reacted quickly to transition infected systems over to a new command and control infrastructure.

“They were clearly reacting and trying to maintain control over components of the botnet,” Adamitis said. “Probably, they wanted to keep that revenue stream going.”

Frustratingly, Lumen was not able to determine how the SOHO devices were being infected with AVrecon. Some possible avenues of infection include exploiting weak or default administrative credentials on routers, and outdated, insecure firmware that has known, exploitable security vulnerabilities.

WHO’S BEHIND SOCKSESCORT?

KrebsOnSecurity briefly visited SocksEscort last year and promised a follow-up on the history and possible identity of its proprietors. A review of the earliest posts about this service on Russian cybercrime forums suggests the 12-year-old malware proxy network is tied to a Moldovan company that also offers VPN software on the Apple Store and elsewhere.

SocksEscort began in 2009 as “super-socks[.]com,” a Russian-language service that sold access to thousands of compromised PCs that could be used to proxy traffic. Someone who picked the nicknames “SSC” and “super-socks” and email address “michvatt@gmail.com” registered on multiple cybercrime forums and began promoting the proxy service.

According to DomainTools.com, the apparently related email address “michdomain@gmail.com” was used to register SocksEscort[.]com, super-socks[.]com, and a few other proxy-related domains, including ip-score[.]com, segate[.]org seproxysoft[.]com, and vipssc[.]us. Cached versions of both super-socks[.]com and vipssc[.]us show these sites sold the same proxy service, and both displayed the letters “SSC” prominently at the top of their homepages.

According to cyber intelligence firm Intel 471, the very first “SSC” identity registered on the cybercrime forums happened in 2009 at the Russian language hacker community Antichat, where SSC asked fellow forum members for help in testing the security of a website they claimed was theirs: myiptest[.]com, which promised to tell visitors whether their proxy address was included on any security or anti-spam block lists.

Myiptest[.]com is no longer responding, but a cached copy of it from Archive.org shows that for about four years it included in its HTML source a Google Analytics code of US-2665744, which was also present on more than a dozen other websites.

Most of the sites that once bore that Google tracking code are no longer online, but nearly all of them centered around services that were similar to myiptest[.]com, such as abuseipdb[.]com, bestiptest[.]com, checkdnslbl[.]com, dnsbltools[.]com and dnsblmonitor[.]com.

Each of these services were designed to help visitors quickly determine whether the Internet address they were visiting the site from was listed by any security firms as spammy, malicious or phishous. In other words, these services were designed so that proxy service users could easily tell if their rented Internet address was still safe to use for online fraud.

Another domain with the Google Analytics code US-2665744 was sscompany[.]net. An archived copy of the site says SSC stands for “Server Support Company,” which advertised outsourced solutions for technical support and server administration.

Leaked copies of the hacked Antichat forum indicate the SSC identity registered on the forum using the IP address 71.229.207.214. That same IP was used to register the nickname “Deem3n®,” a prolific poster on Antichat between 2005 and 2009 who served as a moderator on the forum.

There was a Deem3n® user on the webmaster forum Searchengines.guru whose signature in their posts says they run a popular community catering to programmers in Moldova called sysadmin[.]md, and that they were a systems administrator for sscompany[.]net.

That same Google Analytics code is also now present on the homepages of wiremo[.]co and a VPN provider called HideIPVPN[.]com.

Wiremo sells software and services to help website owners better manage their customer reviews. Wiremo’s Contact Us page lists a “Server Management LLC” in Wilmington, DE as the parent company. Server Management LLC is currently listed in Apple’s App Store as the owner of a “free” VPN app called HideIPVPN.

“The best way to secure the transmissions of your mobile device is VPN,” reads HideIPVPN’s description on the Apple Store. “Now, we provide you with an even easier way to connect to our VPN servers. We will hide your IP address, encrypt all your traffic, secure all your sensitive information (passwords, mail credit card details, etc.) form [sic] hackers on public networks.”

When asked about the company’s apparent connection to SocksEscort, Wiremo responded, “We do not control this domain and no one from our team is connected to this domain.” Wiremo did not respond when presented with the findings in this report.