Google warns of LLMjacking: stolen AI access running up huge cloud bills

Google Threat Intelligence Group says Mandiant responded to multiple incidents in 2026 in which attackers hijacked companies' access to large language models, a tactic it calls LLMjacking, in sectors including financial services, retail, technology and transportation. In some incidents fraudulent charges exceeded $100,000 in a single day, and cumulative charges at some organisations reached $1 million before access was revoked. The most common way in was exposed or stolen cloud credentials, and some groups resell the stolen access through what Google calls LLM Mixers. Google's advice includes spending caps, per-model API quotas, secret scanning in code repositories and alerts when AI services are switched on.