Anthropic removes secret tracker monitoring Chinese Claude Code users after researcher exposes hidden surveillance

Anthropic quickly removed a hidden tracker from Claude Code that secretly monitored users in China after security researcher 'Thereallo' exposed the code, which used prompt steganography to conceal tracking. The tracker flagged users’ timezone, proxy, and potential links to Chinese AI labs that Anthropic has accused of distillation attacks. Anthropic engineer Thariq Shihipar confirmed the tracker was an experiment added in March to prevent account abuse from unauthorized resellers and protect against distillation, noting that such resellers had been selling access to Claude models at drastically reduced prices.