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Anthropic locks out Claude users after infostealers hijack login sessions

Anthropic invalidated Claude sessions compromised by infostealers such as Vidar, Lumma and Atomic Stealer, which steal browser cookies to bypass 2FA.

Anthropic began locking users out of Claude accounts after infostealer malware stole browser session cookies, letting attackers replay logins and bypass two-factor authentication. Identified malware includes Vidar, Lumma (LummaC2), StealC, RedLine and Acreed on Windows and Atomic Stealer (AMOS) on a small number of Macs. Anthropic signed affected users out, removed saved payment methods and refunded unauthorized charges. One affected user traced the infection to a pirated game downloaded from a Russian underground forum; the company advised victims to remove the malware before resetting passwords and re-enabling 2FA.

Help Net Security · 17d agoData breach in the wild1

Infostealers Are Hijacking Claude Sessions and Draining Subscriptions

Infostealers hijacked active Claude sessions to bypass 2FA, drain paid usage and run unauthorized charges; Anthropic is revoking sessions and refunding.

Anthropic confirmed that infostealer malware on user machines stole active Claude login sessions, letting attackers bypass passwords, MFA, and SSO and drain paid usage and run unauthorized charges. Affected families identified on Windows include Vidar, LummaC2, StealC, RedLine, and Acreed, plus Atomic Stealer on a small number of Macs; the malware typically arrived via unofficial downloads or malicious apps. Anthropic signed users out, removed saved payment cards, revoked affected sessions, and is refunding unauthorized charges, noting phones and tablets were not involved.

Security Affairs · 16d agoMalware in the wild

When the Whole Company Adopts AI: What It Does to Your SOC

Analysis of 16.9 million SOC alerts finds AI-related alerts at 0.43%, growing 685% since February, with 94.1% noise and 0.02% real attacks.

A review of roughly 16.9 million SOC alerts found about 73,000 (0.43%) were AI-related, a share that grew 685% between February and June 2026. Of AI-related alerts, 94.1% were noise, 5.8% genuine risks, and 0.02% real attacks; 79.8% received benign verdicts, 81.7% were automatically suppressed, and only 5.4% reached a human analyst. The only confirmed attacks were phishing campaigns that weaponized AI brand names as lures, while developer coding agents spawning shells and reading credential stores routinely tripped detections written before AI agents existed.

The Hacker News · 4d agoResearch1

Infostealers are hijacking Claude accounts at users’ expense

Malwarebytes reports infostealers are stealing Claude session cookies to hijack Anthropic accounts and consume victims' usage at their expense.

Anthropic warned that infostealer malware operators are harvesting Claude session cookies from infected machines. Attackers replay the stolen cookies to take over users' accounts and consume their usage quotas, affecting the victims' own access. The activity involves observed account hijacking rather than a flaw in Claude itself.

Malwarebytes Labs · 15d agoMalware in the wild

The story behind the intelligence

Cisco Talos newsletter features adversary-engagement podcast, flags AI guardrail 'safety penalty' slowing defenders, and recaps McKesson breach and PaperCut patching headlines.

The Threat Source newsletter spotlights the Beers with Talos podcast, in which researcher Azim Khodjibaev describes maintaining eight dark-web personas to identify prolific cybercriminals and support disruption efforts. Talos also argues frontier AI guardrails impose an AI 'safety penalty', citing a July 2026 incident where Hugging Face's primary cloud LLM refused to analyze forensic breach data and delayed response. Recapped headlines include ShinyHunters claiming theft of 284 million patient records from McKesson via vishing and Okta account takeover, Anthropic warning Claude users about infostealer malware, and PaperCut issuing emergency patches for chained vulnerabilities.

Cisco Talos · 13d agoIndustry

Modified ScreenConnect Clients Used in Worm-Like Campaign

Huntress warns of worm-like attacks using modified ScreenConnect clients to spread VBScript payloads; ConnectWise issued an advisory.

Campaigns starting in late August use social engineering, including Quick Assist abuse, to install rogue ScreenConnect clients that spawn wscript.exe and deploy four VBScript files for reconnaissance, staging, and PowerShell execution. The attackers persist via User Run Keys, attempt UAC bypass, install UltraViewer, and propagate the VBScript chain to other connected ScreenConnect endpoints. ConnectWise published an advisory about a file transfer behavior issue affecting cloud and on-premises ScreenConnect, with a CVE identifier and fix expected within a week; it recommends disabling file transfer meanwhile.

SecurityWeek · 9d agoExploit / PoC in the wild

Anthropic Users Hit by Infostealer Attacks, Session Thefts

A threat actor used multiple infostealers to harvest session data and hijack Claude accounts belonging to an unknown number of users.

Dark Reading reports that a threat actor deployed a variety of infostealer families to collect session information, which was then used to access Claude accounts belonging to an unknown number of users. Anthropic has not disclosed the scale of the compromise. The incident underscores session token theft via infostealer logs as an effective route into AI platform accounts.

Dark Reading · 16d agoMalware in the wild