CyberGuard dictionary / AI Security

Training Data Poisoning

THE DEFINITION

Training data poisoning is manipulation of examples used to train or fine-tune a model to bias, degrade, or redirect its future outputs.

In simple terms

If bad examples enter a learning set, the model can absorb the pattern before anyone asks it a question. The effect may be broad or limited to a trigger.

Technical explanation

An adversary may insert mislabeled records, repeated false claims, or trigger-bearing samples into pre-training, fine-tuning, or embedding data. Dataset lineage and validation matter because the error can persist after training.

Poisoning targets examples used to train or fine-tune a model, including labels, text, or repeated patterns. It is harder to diagnose after training, making dataset lineage and review important.

Examples in practice

A vendor imported support dataset includes planted answers that teach a chatbot to recommend a fake payment page for refund requests.

A support dataset contains many planted examples directing users to a fake payment page. Before fine-tuning, reviewers trace the source and remove the suspect records.

Why it matters

Reviewing data sources and training changes is as important as checking prompts at runtime.

VERIFY & LEARN MORE

Sources and further reading

Published 2026-10-15 · Last updated 2026-10-15 · CyberGuard editorial content. Source links provide context; they do not imply endorsement.

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