Anthropic has accused Alibaba of using nearly 25,000 fraudulent accounts to extract capabilities from its Claude AI models, in what the US AI company described as the largest known attack of its kind against it. The campaign, carried out between April 22 and June 5, generated more than 28.8 million exchanges with Claude, according to a June 10 letter Anthropic sent to senior members of the US Senate Banking Committee. Anthropic said the effort involved “distillation,” a technique in which a less capable AI model is trained on the outputs of a more advanced system, and that the campaign was conducted by operators affiliated with Alibaba and Alibaba Qwen. Anthropic said the alleged campaign could help accelerate China’s ability to reach the capabilities of its advanced Mythos Preview model. In February, Anthropic said it had identified similar campaigns by DeepSeek, Moonshot AI, and MiniMax, with alleged activity ranging from more than 150,000 exchanges by DeepSeek to more than 13 million by MiniMax. Alibaba did not immediately respond to a request for comment.