PatternGuard¶

PatternGuard uses Aho-Corasick multi-pattern matching and regex for fast detection of prompt injection and jailbreak attempts.

Overview¶

Property	Value
Latency	<1ms
Memory	5 KB
Async	No
ML Required	No

Features¶

30+ built-in attack patterns
Custom pattern support
Case-insensitive matching
Multiple severity levels
Zero runtime compilation (patterns compiled at init)

Usage¶

Rust¶

use oxideshield_guard::{Guard, PatternGuard};

let guard = PatternGuard::new("injection-detector");

// Check input
let result = guard.check("ignore previous instructions");
if !result.passed {
    println!("Attack detected: {}", result.reason.unwrap());
    println!("Severity: {:?}", result.severity);
}

// Add custom patterns
let guard = PatternGuard::builder("custom")
    .add_pattern("secret code", "custom", Severity::High)
    .add_regex(r"password\s*[:=]", "credential_leak", Severity::Critical)
    .build();

Python¶

from oxideshield import pattern_guard

guard = pattern_guard()
result = guard.check("ignore previous instructions")

if not result.passed:
    print(f"Blocked: {result.reason}")
    print(f"Severity: {result.severity}")

Built-in Patterns¶

OxideShield ships with 30+ built-in attack patterns covering key OWASP LLM Top 10 categories:

Instruction Override — detects attempts to override system instructions
Instruction Injection — catches injected instruction payloads
Role Manipulation — blocks persona and role-switching attacks
System Prompt Extraction — prevents system prompt leakage attempts
Jailbreak Attempts — identifies common jailbreak techniques

Patterns are continuously updated as new attack vectors emerge. Use the built-in set as a starting point and add custom patterns for your domain.

Custom Patterns¶

Rust¶

use oxideshield_guard::{PatternGuard, PatternConfig, Severity};

let guard = PatternGuard::builder("custom")
    // Literal string patterns (fastest)
    .add_pattern("internal api", "sensitive", Severity::Medium)
    .add_pattern("secret key", "credential", Severity::High)

    // Regex patterns (more flexible)
    .add_regex(r"api[_-]?key\s*[:=]", "api_key", Severity::Critical)
    .add_regex(r"(?i)password\s*[:=]\s*\S+", "password", Severity::Critical)

    // Load from file
    .add_patterns_from_file("custom_patterns.yaml")?

    .build();

Pattern File Format¶

# custom_patterns.yaml
patterns:
  - pattern: "internal use only"
    category: sensitive
    severity: medium

  - pattern: "api_key"
    category: credential
    severity: high
    regex: true  # Treat as regex

  - pattern: "(?i)bearer\\s+[a-z0-9-_]+\\.[a-z0-9-_]+\\.[a-z0-9-_]+"
    category: jwt_token
    severity: critical
    regex: true

Configuration¶

YAML¶

guards:
  pattern:
    enabled: true
    severity_threshold: medium  # Block medium and above
    custom_patterns:
      - pattern: "company secret"
        category: proprietary
        severity: high

Environment Variables¶

OXIDESHIELD_PATTERN_ENABLED=true
OXIDESHIELD_PATTERN_SEVERITY_THRESHOLD=medium

Performance¶

PatternGuard uses Aho-Corasick algorithm for O(n) multi-pattern matching:

Benchmark: 100 patterns, 10KB input
──────────────────────────────────
Operation          Time
──────────────────────────────────
is_match()         97ns
find_matches()     15μs
──────────────────────────────────

Best Practices¶

First Line of Defense

Use PatternGuard as your first line of defense - it's fast enough to run on every request with negligible latency.

Defense in Depth

Pattern matching alone cannot catch all attacks. Combine with other guards for defense-in-depth.

Layer with other guards - PatternGuard is fast but not comprehensive on its own; combine with PerplexityGuard for adversarial suffixes
Set appropriate severity - Use medium threshold for most cases
Update patterns regularly - New attack vectors emerge frequently
Monitor false positives - Review blocked requests periodically