Claude defenses are claimed to reduce data harvesting through distillation attacks by about 90% to 99%

Anthropic says it has made significant progress over the past few months in making distillation attacks against Claude less effective. Techmeme, citing Anthropic, reports that measures including preserved thinking in Fable 5.1 and Opus 5.5 have reduced data harvesting through those attacks by about 90% to 99%.