Krebs on Security

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mostly consumer-grade routers, security cameras, digital video recorders and other devices operating with insecure and outdated firmware, and/or factory-default settings.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.”

Krebs on Security

Oregon Man Charged in ‘Rapper Bot’ DDoS Service

A 22-year-old Oregon man has been arrested on suspicion of operating “Rapper Bot,” a massive botnet used to power a service for launching distributed denial-of-service (DDoS) attacks against targets — including a March 2025 DDoS that knocked Twitter/X offline. The Justice Department asserts the suspect and an unidentified co-conspirator rented out the botnet to online extortionists, and tried to stay off the radar of law enforcement by ensuring that their botnet was never pointed at KrebsOnSecurity.

On August 6, 2025, federal agents arrested Ethan J. Foltz of Springfield, Ore. on suspicion of operating Rapper Bot, a globally dispersed collection of tens of thousands of hacked Internet of Things (IoT) devices.

The complaint against Foltz explains the attacks usually clocked in at more than two terabits of junk data per second (a terabit is one trillion bits of data), which is more than enough traffic to cause serious problems for all but the most well-defended targets. The government says Rapper Bot consistently launched attacks that were “hundreds of times larger than the expected capacity of a typical server located in a data center,” and that some of its biggest attacks exceeded six terabits per second.

Indeed, Rapper Bot was reportedly responsible for the March 10, 2025 attack that caused intermittent outages on Twitter/X. The government says Rapper Bot’s most lucrative and frequent customers were involved in extorting online businesses — including numerous gambling operations based in China.

The criminal complaint was written by Elliott Peterson, an investigator with the Defense Criminal Investigative Service (DCIS), the criminal investigative division of the Department of Defense (DoD) Office of Inspector General. The complaint notes the DCIS got involved because several Internet addresses maintained by the DoD were the target of Rapper Bot attacks.

Peterson said he tracked Rapper Bot to Foltz after a subpoena to an ISP in Arizona that was hosting one of the botnet’s control servers showed the account was paid for via PayPal. More legal process to PayPal revealed Foltz’s Gmail account and previously used IP addresses. A subpoena to Google showed the defendant searched security blogs constantly for news about Rapper Bot, and for updates about competing DDoS-for-hire botnets.

According to the complaint, after having a search warrant served on his residence the defendant admitted to building and operating Rapper Bot, sharing the profits 50/50 with a person he claimed to know only by the hacker handle “Slaykings.” Foltz also shared with investigators the logs from his Telegram chats, wherein Foltz and Slaykings discussed how best to stay off the radar of law enforcement investigators while their competitors were getting busted.

Specifically, the two hackers chatted about a May 20 attack against KrebsOnSecurity.com that clocked in at more than 6.3 terabits of data per second. The brief attack was notable because at the time it was the largest DDoS that Google had ever mitigated (KrebsOnSecurity sits behind the protection of Project Shield, a free DDoS defense service that Google provides to websites offering news, human rights, and election-related content).

The May 2025 DDoS was launched by an IoT botnet called Aisuru, which I discovered was operated by a 21-year-old man in Brazil named Kaike Southier Leite. This individual was more commonly known online as “Forky,” and Forky told me he wasn’t afraid of me or U.S. federal investigators. Nevertheless, the complaint against Foltz notes that Forky’s botnet seemed to diminish in size and firepower at the same time that Rapper Bot’s infection numbers were on the upswing.

“Both FOLTZ and Slaykings were very dismissive of attention seeking activities, the most extreme of which, in their view, was to launch DDoS attacks against the website of the prominent cyber security journalist Brian Krebs,” Peterson wrote in the criminal complaint.

“You see, they’ll get themselves [expletive],” Slaykings wrote in response to Foltz’s comments about Forky and Aisuru bringing too much heat on themselves.

“Prob cuz [redacted] hit krebs,” Foltz wrote in reply.

“Going against Krebs isn’t a good move,” Slaykings concurred. “It isn’t about being a [expletive] or afraid, you just get a lot of problems for zero money. Childish, but good. Let them die.”

“Ye, it’s good tho, they will die,” Foltz replied.

The government states that just prior to Foltz’s arrest, Rapper Bot had enslaved an estimated 65,000 devices globally. That may sound like a lot, but the complaint notes the defendants weren’t interested in making headlines for building the world’s largest or most powerful botnet.

Quite the contrary: The complaint asserts that the accused took care to maintain their botnet in a “Goldilocks” size — ensuring that “the number of devices afforded powerful attacks while still being manageable to control and, in the hopes of Foltz and his partners, small enough to not be detected.”

The complaint states that several days later, Foltz and Slaykings returned to discussing what that they expected to befall their rival group, with Slaykings stating, “Krebs is very revenge. He won’t stop until they are [expletive] to the bone.”

“Surprised they have any bots left,” Foltz answered.

“Krebs is not the one you want to have on your back. Not because he is scary or something, just because he will not give up UNTIL you are [expletive] [expletive]. Proved it with Mirai and many other cases.”

[Unknown expletives aside, that may well be the highest compliment I’ve ever been paid by a cybercriminal. I might even have part of that quote made into a t-shirt or mug or something. It’s also nice that they didn’t let any of their customers attack my site — if even only out of a paranoid sense of self-preservation.]

Foltz admitted to wiping the user and attack logs for the botnet approximately once a week, so investigators were unable to tally the total number of attacks, customers and targets of this vast crime machine. But the data that was still available showed that from April 2025 to early August, Rapper Bot conducted over 370,000 attacks, targeting 18,000 unique victims across 1,000 networks, with the bulk of victims residing in China, Japan, the United States, Ireland and Hong Kong (in that order).

According to the government, Rapper Bot borrows much of its code from fBot, a DDoS malware strain also known as Satori. In 2020, authorities in Northern Ireland charged a then 20-year-old man named Aaron “Vamp” Sterritt with operating fBot with a co-conspirator. U.S. prosecutors are still seeking Sterritt’s extradition to the United States. fBot is itself a variation of the Mirai IoT botnet that has ravaged the Internet with DDoS attacks since its source code was leaked back in 2016.

The complaint says Foltz and his partner did not allow most customers to launch attacks that were more than 60 seconds in duration — another way they tried to keep public attention to the botnet at a minimum. However, the government says the proprietors also had special arrangements with certain high-paying clients that allowed much larger and longer attacks.

Most people who have never been on the receiving end of a monster DDoS attack have no idea of the cost and disruption that such sieges can bring. The DCIS’s Peterson wrote that he was able to test the botnet’s capabilities while interviewing Foltz, and that found that “if this had been a server upon which I was running a website, using services such as load balancers, and paying for both outgoing and incoming data, at estimated industry average rates the attack (2+ Terabits per second times 30 seconds) might have cost the victim anywhere from $500 to $10,000.”

“DDoS attacks at this scale often expose victims to devastating financial impact, and a potential alternative, network engineering solutions that mitigate the expected attacks such as overprovisioning, i.e. increasing potential Internet capacity, or DDoS defense technologies, can themselves be prohibitively expensive,” the complaint continues. “This ‘rock and a hard place’ reality for many victims can leave them acutely exposed to extortion demands – ‘pay X dollars and the DDoS attacks stop’.”

The Telegram chat records show that the day before Peterson and other federal agents raided Foltz’s residence, Foltz allegedly told his partner he’d found 32,000 new devices that were vulnerable to a previously unknown exploit.

Shortly before the search warrant was served on his residence, Foltz allegedly told his partner that “Once again we have the biggest botnet in the community.” The following day, Foltz told his partner that it was going to be a great day — the biggest so far in terms of income generated by Rapper Bot.

“I sat next to Foltz while the messages poured in — promises of $800, then $1,000, the proceeds ticking up as the day went on,” Peterson wrote. “Noticing a change in Foltz’ behavior and concerned that Foltz was making changes to the botnet configuration in real time, Slaykings asked him ‘What’s up?’ Foltz deftly typed out some quick responses. Reassured by Foltz’ answer, Slaykings responded, ‘Ok, I’m the paranoid one.”

The case is being prosecuted by Assistant U.S. Attorney Adam Alexander in the District of Alaska (at least some of the devices found to be infected with Rapper Bot were located there, and it is where Peterson is stationed). Foltz faces one count of aiding and abetting computer intrusions. If convicted, he faces a maximum penalty of 10 years in prison, although a federal judge is unlikely to award anywhere near that kind of sentence for a first-time conviction.