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Google’s Mandiant and Threat Intelligence Group (GTIG) say attackers are hijacking enterprise access to large language models and running up huge fraudulent cloud charges.

Google’s report documents more than $100,000 in a single day. At some organizations, cumulative charges reached $1 million before they revoked access.

Mandiant responded to multiple 2026 incidents across North America, South America, and Asia Pacific. Victims included financial services, retail, technology, and transportation.

Unlike gradual cryptojacking, LLMJacking can produce massive billing spikes within hours. GTIG also tracks a division of labor between initial access actors and “LLM Mixers,” illicit gateways that proxy, pool, and resell stolen LLM access to underground subscribers.

Attackers bypass front-end chatbots and target backend model resources directly. They scan for exposed endpoints, such as Ollama servers, and try to register their own models through /api/create. The dominant vector, however, is exposed or stolen cloud identity tokens, including IAM credentials, service account keys, GitHub personal access tokens, and session tokens.

UNC6993 compromised a cloud instance through a misconfigured service account key. It also hosted a fake portal that tricked users into pasting raw JSON session tokens, bypassing passwords and MFA.

Another actor harvested LLM API keys from public GitHub repositories and validated them with max_tokens=1 requests to avoid EDR and SIEM alerts. Earlier research on LLMjacking with stolen AWS non-human identities shows this credential-driven pattern is not new.

After entry, actors created rogue IAM and service accounts, injected SSH keys into compute metadata, and pulled secrets from cloud secret managers. A follow-on cluster abused a user ID rebind flaw in LiteLLM’s /key/regenerate endpoint (CVE-2026-40217) to elevate virtual keys to PROXY_ADMIN. This matches a wider trend of attackers exploiting exposed MCP services and LiteLLM gateways.

UNC6993 enabled managed AI services and created extra API keys, quickly accumulating over $100,000 in charges. It used open-source tools such as new-api and gcli2api, likely to pool stolen keys.

Another actor made over 500,000 API calls in under eight hours to power jet-night.com, passing nearly $1 million in costs to the victim. Jet Night sold an “unlimited” plan for about $60 a month, a price GTIG says points to stolen keys. The PoeLLM campaign likewise shows attackers hijacking exposed AI infrastructure for profit.

Google recommends implementing a centralized secrets management system that includes automatic key rotation. Access should be based on the principle of least privilege, denying access to LLM services unless necessary.

It’s also essential to scan code repositories for secrets. Organizations should also set API quotas, establish spending limits, and enable budget alerts. Use phishing-resistant multi-factor authentication (MFA) across all cloud identity providers and consoles.

Defenders should scope API keys based on the specific model and environment, while actively monitoring logs for low-volume validation requests, such as those with max_tokens=1. Patch gateways like LiteLLM promptly. Any unauthorized activation of services such as Bedrock or the Gemini API should be treated as a serious event.

The GTIG anticipates that attackers will prefer LLMJacking over cryptojacking. LLM mixers offer them quick, high-margin profits, and enterprises are increasingly incorporating higher-tier models and agent-driven workflows.

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