Glossary
Defense in Depth
A layered security strategy applying multiple independent safeguards to protect AI agent systems against threats and failures.
What is Defense in Depth?
Defense in depth assumes no single security measure is perfect, instead deploying multiple overlapping controls at different system layers. For agent systems, this includes input validation, prompt filtering, output screening, access controls, network segmentation, monitoring, and audit logging. Each layer provides independent protection, so breaching one control does not compromise the entire system.
This approach is particularly important for AI agents because they interact with unpredictable inputs and can be exploited in novel ways. Layered defenses catch different attack types: input filters block obvious prompt injections, guardrails prevent policy violations, output screening catches sensitive data leaks, and monitoring detects anomalous behavior patterns. The redundancy provides resilience even when individual controls fail or are bypassed.
Example
A customer service agent has input sanitization to block code injection, content filters preventing PII disclosure, rate limiting to prevent abuse, network rules restricting API access, real-time monitoring for unusual behavior, and immutable audit logs. An attacker bypassing input validation is still blocked by output filters and flagged by monitoring.
How Signet addresses this
Signet's Security dimension evaluates the depth and quality of security controls. Agents implementing comprehensive layered security with multiple independent safeguards achieve higher security scores than those relying on single-point defenses.
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