Poisoning Attacks on LLMs Require a Near-Constant Number of Poison Samples
Date: 2025-10
Affected: Pre-trained LLMs across multiple scales
Attack vector: model-poisoning
Category: research
Severity: Critical

Anthropic/UK AISI joint study shows that successful LLM pre-training poisoning requires only a roughly constant number (around 250) of poisoned documents regardless of model or dataset size, overturning the percent-of-corpus mental model.


Mitigations:

Architectural layers (MAESTRO):