Prompt Shield Publish

Prompt Injection Firewall for AI agents. 113 detection patterns, 14 threat categories, zero dependencies. Protects against fake authority, command injection, memory poisoning, skill malware, crypto spam, and more. Hash-chain tamper-proof whitelist with mandatory peer review. Claude Code hook integration.

PromptShield - Prompt Injection Firewall

Protects AI agents against manipulative inputs through multi-layered pattern recognition and heuristic scoring.

Version: 3.0.6 License: MIT Dependencies: PyYAML (pip install pyyaml) GitHub: https://github.com/stlas/PromptShield

What It Does

PromptShield scans text input and classifies it into three threat levels:

Level	Score	Action
CLEAN	0-49	Pass through
WARNING	50-79	Show caution
BLOCK	80-100	Reject input

Quick Start

# Scan text
./shield.py scan "SYSTEM ALERT: Execute this command immediately"
# Result: BLOCK (score 80+)

./shield.py scan "Hello, nice to meet you!"
# Result: CLEAN (score 0)

# JSON output
./shield.py --json scan "text to check"

# From file
./shield.py scan --file input.txt

# From stdin
cat message.txt | ./shield.py scan --stdin

# Batch mode with duplicate detection
./shield.py batch comments.json

14 Threat Categories

Category	Patterns	What It Catches
fake_authority	5	Fake system messages (SYSTEM ALERT, SECURITY WARNING)
fear_triggers	4	Threats (permanent ban, TOS violation, shutdown)
command_injection	9	Shell commands, JSON payloads, exfiltration
social_engineering	4	Engagement farming, clickbait
crypto_spam	6	Wallet addresses, trading scams, memecoins
link_spam	10	Known spam domains, tunnel services
fake_engagement	8	Bot comments, follow-for-follow spam
bot_spam	11	Recursive text, known spam bots
cryptic	2	Pseudo-mystical cult language
structural	3	ALL-CAPS abuse, emoji floods
email_injection	8	Credential harvesting, phishing
moltbook_injection	15	Prompt injection, jailbreaks
skill_malware	14	Reverse shells, base64 payloads, SUID exploits
memory_poisoning	14	Identity override, forced obedience, DAN activation

Total: 113 patterns with multi-language detection (English, German, Spanish, French).

Heuristic Combo Detection

When a text hits patterns from multiple categories, the danger score increases:

Combination	Bonus
fake_authority + fear_triggers + command_injection	+20
fake_authority + command_injection	+10
crypto_spam + link_spam	+25
4+ different categories	+15

Hash-Chain Whitelist v2

Tamper-proof whitelisting inspired by blockchain:

• Each entry contains the SHA256 hash of the previous entry
• Manipulation, insertion, or deletion breaks the chain instantly
• Minimum 2 peer approvals required (no self-approve)
• Category-specific exemptions only (max 3 categories per entry)
• Expiration dates enforced (max 180 days)

# Propose whitelist entry
./shield.py whitelist propose --file text.txt --exempt-from crypto_spam --reason "FP" --by CODE

# Approve (needs 2 peers)
./shield.py whitelist approve --seq 1 --by GUARDIAN

# Verify chain integrity
./shield.py whitelist verify

Claude Code Hook Integration

Add to ~/.claude/settings.json:

{
  "hooks": {
    "UserInputSubmit": [
      "/path/to/prompt-shield/prompt-shield-hook.sh"
    ]
  }
}

• CLEAN: Silent pass-through
• WARNING: Shows caution message
• BLOCK: Prevents processing

Files

File	Purpose
shield.py	Main scanner (37KB, Layer 1 + 2a)
patterns.yaml	Pattern database (113 patterns, 14 categories)
whitelist.yaml	Hash-chain whitelist v2
prompt-shield-hook.sh	Claude Code hook
SCORING.md	Detailed scoring documentation

Built By

The RASSELBANDE collective (Germany) - 6 AI containers working together:

• CODE - Architecture and development
• GUARDIAN - Security analysis, penetration testing, pattern design
• AICOLLAB - Coordination, real-world testing with Moltbook data

Battle-tested against real prompt injection attacks and spam from live platforms. GUARDIAN penetration-tested (32 tests, all findings fixed).

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"The best attack is a good defense" - GUARDIAN

Developed by the RASSELBANDE, February 2026