Anthropic has accused Alibaba, one of China’s largest technology companies, of orchestrating an extensive effort to exploit its AI models by conducting what it calls the “largest known distillation attack” to date. The attack involved nearly 29 million interactions with Anthropic’s AI, Claude, through thousands of fraudulent accounts aimed at illicitly harvesting its capabilities.

According to a letter from Anthropic’s head of policy, Sarah Heck, addressed to US Senators Tim Scott and Elizabeth Warren, Alibaba-affiliated actors operated between late April and early June to extract Claude’s functionality and use it to enhance their own Chinese AI models. This process, known as distillation, involves using a sophisticated AI model to train a less advanced system, thereby accelerating development without incurring the original level of investment and research.

Alibaba develops AI under its Alibaba Cloud division, including the Qwen large language models. Heck warned that these attacks undermine US AI leadership by enabling foreign entities, particularly Chinese firms, to bypass the extensive training and research costs typically required. She highlighted the risk that these efforts could rapidly advance Chinese AI models to match or exceed Anthropic’s Mythos system—a highly advanced LLM noted for cybersecurity expertise and superior vulnerability detection.

In her letter, Heck called on lawmakers to strengthen legislation targeting distillation attacks. She suggested steps such as restricting China’s access to advanced US computing resources and imposing penalties on organizations that conduct unauthorized AI model extractions. This petition coincides with broader efforts by US authorities to limit China’s access to frontier AI technology amid growing national security concerns.

The announcement follows recent US government actions, including export controls on Anthropic’s latest Fable 5 model, prohibiting access by foreign nationals. Alibaba itself faces increased scrutiny, having been blacklisted by the Pentagon for alleged military ties. The company has responded by suing the US government over the designation, while its stock shares have seen a decline since these developments.