# How to prevent prompt injection, tested across 13 attacks and four models

> Original title: How to Prevent Prompt Injection: 13 Attacks, Tested

- Source: OpenRouter Blog
- Published: 2026-10-29T00:00:00.000Z
- Bad Influence: https://badinfluence.news/items/tqm9t12shw6tsrnct4w4ooofd
- Original: https://openrouter.ai/blog/tutorials/prevent-prompt-injection/

## Summary

OpenRouter tested 25 prompt injection attacks, 13 written by its team and 12 by other models, against four current models with each defense switched on and off. With its Armor tool-call checker enabled, attack emails dropped from 73 of 1,440 attempts to 0, while nearly all legitimate emails still went through. Labeling untrusted documents as data cut attack emails from 60 to 13 of 720 attempts, and the team found one model sent 58 of the 60 attack emails with no defenses.