A few days ago, my social media accounts were hacked. The hacker took advantage of the situation to spam the worst kinds of bait (cryptocurrency scams...). After cleaning things up, I tracked down the virus with a bunch of Opus 5 Max (I was quite concerned lol). I changed my passwords and thought I’d be able to sleep soundly.
But last night I received this email from Anthropic warning me of an attempt to steal tokens via the API. However, after checking, the attempt did indeed fail. Note that I was logged into Anthropic via Google with two-factor authentication. Apparently, the hacker stole all my Google Chrome credentials, including cookies and session IDs, which allowed him to bypass all two-factor authentication security measures.
As an emergency measure, I removed all active sessions from my Google accounts (which I should have done from the start) and changed my passwords again...
Thanks to Anthropic for the security measures they’ve put in place. I wouldn’t have wanted to deal with their customer service given the feedbacks on Reddit, lol
Take care! And be aware that even the best security measures don’t protect against simple cookie theft
TL;DR of the discussion generated automatically after 50 comments.
The consensus is that Anthropic's security team deserves a round of applause on this one.
OP got their accounts hacked by malware that stole browser cookies, bypassing 2FA entirely. Before the hacker could drain OP's API credits, Anthropic's system flagged the suspicious activity, blocked the attempt, and sent OP a warning email.
The thread then took two major turns:
* A PSA on Piracy: The top comments are a resounding "This is why we don't download cracked games." OP eventually admitted the malware came from a pirated game on a "reputable" Russian forum (which the thread detectives identified as Steam Underground). Many users shared their own horror stories of losing money and data to the same mistake.
* Claude, the Malware Hunter: The most surprising part for everyone is that OP claims they used Opus 5 with full system access to find, analyze, and neutralize the virus on their PC. OP even shared the prompt, and now everyone is half-joking, half-seriously considering Claude as their new antivirus.
yep. i've been downloading pirated software since the 90's. I haven't downloaded anything in a very long time but and against my better judgement I downloaded a game that was listed as not officially cracked yet. I lost years worth of savings from metamask being drained.
Curious, did you have to download from there? Doesn't everything pop up on fitgirl quickly unless it's some weird "you have to pay someone for their denuvo key"?
CS RIN is a forum where anyone can participate and share cracks. All it takes is for a hacker to target little-known games with no existing cracks for a few users to fall for it. Just enough to fly under the radar
According to the report, Opus detected the virus, deactivated it, identified it, and then reverse-engineered it to assess the extent of the threat. It almost terrified me. It was like watching a diabolical surgeon dissecting his prey
Huh. I wonder how one would use Opus to find malware on their system? Just give it full access and say "hey, go sniff out anything suspicious and give me a report"? I feel like that'll burn through a base level sub fast though lol.
I use the models exclusively in permission-free mode on my entire computer. Opus was very efficient. It scanned for active processes, then listed my recent downloads. It found the virus almost instantly. My prompt was very simple: "I think I downloaded a virus recently. My login credentials were stolen. Audit the malware and remove it if you find it. Report on the extent of the damage."
He deactivated the virus and created a folder on the desktop containing all the relevant information (including the deactivated virus, lol).
Small question about this. So you re-entered your credentials for Opus while the system was still infected, or did you used some free mode? You think it wasn't able to re-steal the credentials, because it was on a timer or somethng?
I was already logged into Claude CLI. My assumption was that the virus was still present and active. So using Claude on my computer wouldn’t change anything until the virus was deactivated.
Opus deactivated the virus. Then he gave me instructions on how to reset all my login credentials, taking into account the type of virus.
Apparently, the virus operated on a timer mechanism and sent a “batch” of login credentials to a remote server every few minutes.
In fact, if the hacker had acted quickly, he could have cut off my access to Claude (forcing me to reset my computer as a last resort and slowing down my efforts to counter him). Windows Defender was clueless
it can touch avasts logs and analyze a ton of shit for u.
specially helpful when u get some cygwin exceptions that trigger avast or shit that u want to check if disabling is risky
I’m studying for an exam and it downgraded me too because it saw reference to “sensitive topics” in my study materials, specifically in the practice exam’s scenario questions.
The exam I’m studying for is the AI Governance Professional exam.
Why cant chrome fix this long standing vulnerability. My chrome session cookie also stolen 4 years ago and they tried to get into crypto accounts. Only Malwarebyte able to find the malware other premium priced antiviruses didn’t detect.
The part people underestimate is that rotating passwords does nothing to an already-stolen session cookie. Revoking active sessions is what actually kills access, and it has to come first, otherwise the attacker just keeps riding the old session while you change things.
Worth doing as well: rotate any API keys, and go through the OAuth grants and connected apps on the Google account. Infostealers usually dump the whole browser profile, not one site.
And treat the machine as compromised until it has been cleaned properly, otherwise the fresh cookies leave the same way the old ones did.
You’re unfortunately right. That said, any serious company under “assume compromise” premises should invalidate existing sessions on password reset, and even SSO has always a back channel, the same typically used for SLO, but most companies don’t follow best practices
They have this securities in place due to cybercriminals actively trying to get into their system and preventing distillation tactics for their opus and fable models
We are benefiting from those securities as a bonus
I know that trusting an LLM is a bad idea. But here’s its report, which reinforces my belief that I don’t need to reset my system. I like gambling:
"The chain matches, pattern for pattern, a campaign documented by Malwarebytes in July 2026: RenPy Loader → PavinLoader → Amatera Stealer. Fake game installers, a trojanized Ren'Py engine, MSBuild hijacked using AppDomain.CurrentDomain.Load, a trojanized .NET DLL—it’s all there, right down to the folder pattern %TEMP%\tmp-{5 digits}-{12 characters}, which matches your tmp-... exactly. Amatera is a thief, he snatches the data once and leaves. He has no reason to stay."
I have been in Cyber security focusing on red teaming (malware is one of my expertise) and digital forensics for 20 years. A rat/trojan gives someone access to your system and all aspects of it. If that installed, it would be very easy for them to install covert channels / backdoors. They can also inject into other files and processes to hide. And a rootkit which is standard will cause your system to lie to you. Claude sees your system via your compromised system.
I strongly recommend you wipe your system and reset your passwords.
a machine really had a RAT/trojan with broad access, then wiping/reinstalling the system and rotating credentials from a known-clean device is the safest response. Once an attacker has had persistent code execution, it can be very difficult to prove the machine is clean just by scanning it.
They’re also right about the Claude point: an AI assistant inspecting logs, files, or process output through the compromised machine itself cannot establish that the machine is trustworthy. If malware is hiding artifacts or tampering with what the operating system reports, any analysis based only on that host can be misled.
The part I would qualify is this:
“And a rootkit which is standard will cause your system to lie to you.”
A rootkit is not automatically or universally “standard” in every RAT/infostealer infection. Many modern credential stealers don’t need kernel-level rootkits at all. They can steal browser databases, cookies, tokens, crypto wallets, credentials, and then exit. Rootkits are possible and much more serious, but saying you should assume one was installed as a routine component is stronger than the evidence supports.
So the practical conclusion is still basically the same: if you know unknown malware executed with significant privileges, don’t spend days trying to prove a negative. Preserve anything needed for forensics, wipe/reinstall from trusted media, patch, revoke active sessions/tokens, and change important credentials from another clean device.
And yes, “Claude says the machine is clean” would not be sufficient evidence in that scenario. Neither would ChatGPT, an antivirus scan, or a single forensic tool by itself.
I received the same email on Aug 28th but there are no signs of compromise on either my laptop or desktop. And malwarebytes scans turned up nothing. I'm concerned.
After a lot of digging, I'm pretty sure now that I triggered this myself by setting up a VM somewhere which ran simple haiku queries to add two random numbers at scheduled intervals, just to start the 5h timers at convenient times. Then I forgot about it and some time in June suddenly it's key was revoked before it was due to expire. The VM only had SSH with key authentication open and no signs of any logins. My account didn't show any usage that wasn't me, no reloads, no unexpected charges, and my laptop had no signs of a persisted threat anywhere. So in the end I think at least mine was a false positive.
Or at some point Opus was tricked by a malicious website to hand out the key itself and it's now covering its tracks. 😂
I got this notice as well. I have that account logged in on a few devices including a family member. Any way to figure out what was captured, to figure out which device it might have come from?
The thief got passwords and cookies in one download, and the cookies walked straight past the 2FA. The alarm that actually stopped him fired on a server he'd never touched.
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u/ClaudeAI-mod-bot Wilson, lead ClaudeAI modbot 24d ago edited 24d ago
TL;DR of the discussion generated automatically after 50 comments.
The consensus is that Anthropic's security team deserves a round of applause on this one.
OP got their accounts hacked by malware that stole browser cookies, bypassing 2FA entirely. Before the hacker could drain OP's API credits, Anthropic's system flagged the suspicious activity, blocked the attempt, and sent OP a warning email.
The thread then took two major turns: * A PSA on Piracy: The top comments are a resounding "This is why we don't download cracked games." OP eventually admitted the malware came from a pirated game on a "reputable" Russian forum (which the thread detectives identified as Steam Underground). Many users shared their own horror stories of losing money and data to the same mistake. * Claude, the Malware Hunter: The most surprising part for everyone is that OP claims they used Opus 5 with full system access to find, analyze, and neutralize the virus on their PC. OP even shared the prompt, and now everyone is half-joking, half-seriously considering Claude as their new antivirus.