Sentinel: SOTA model to protect against prompt injections
Authors: name: Dror Ivry; name: Oran Nahum
Published: 2025-06-05 14:07:15

Abstract: Large Language Models (LLMs) are increasingly powerful but remain vulnerable
to prompt injection attacks, where malicious inputs cause the model to deviate
from its intended instructions. This paper introduces Sentinel, a novel
detection model, qualifire/prompt-injection-sentinel, based on the
\answerdotai/ModernBERT-large architecture. By leveraging ModernBERT's advanced
features and fine-tuning on an extensive and diverse dataset comprising a few
open-source and private collections, Sentinel achieves state-of-the-art
performance. This dataset amalgamates varied attack types, from role-playing
and instruction hijacking to attempts to generate biased content, alongside a
broad spectrum of benign instructions, with private datasets specifically
targeting nuanced error correction and real-world misclassifications. On a
comprehensive, unseen internal test set, Sentinel demonstrates an average
accuracy of 0.987 and an F1-score of 0.980. Furthermore, when evaluated on
public benchmarks, it consistently outperforms strong baselines like
protectai/deberta-v3-base-prompt-injection-v2. This work details Sentinel's
architecture, its meticulous dataset curation, its training methodology, and a
thorough evaluation, highlighting its superior detection capabilities.