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41 lines
1.4 KiB
Markdown
41 lines
1.4 KiB
Markdown
---
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name: hunting-for-webshells-in-web-servers
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description: >-
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Detect webshells planted on web servers by scanning for high-entropy files,
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suspicious PHP/JSP/ASP patterns (eval, base64_decode, system, passthru),
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recently modified files in web roots, and anomalous file sizes. Uses Shannon
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entropy calculation to flag obfuscated payloads and regex pattern matching
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against known webshell signatures.
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domain: cybersecurity
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subdomain: security-operations
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tags: [hunting, for, webshells, web]
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version: "1.0"
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author: mahipal
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license: MIT
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---
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## Instructions
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1. Install dependencies: `pip install yara-python`
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2. Identify web server document roots to scan (e.g., `/var/www/html`, `/opt/lampp/htdocs`).
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3. Run the agent to scan for webshells:
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- Shannon entropy analysis flags files with entropy > 5.5
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- Pattern matching detects eval(), base64_decode(), system(), passthru(), shell_exec()
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- File modification time analysis finds recently changed files
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- Extension filtering targets .php, .jsp, .asp, .aspx, .cgi, .py files
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```bash
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python scripts/agent.py --webroot /var/www/html --output webshell_report.json
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```
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## Examples
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### High-Entropy PHP Webshell Detection
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```
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File: /var/www/html/uploads/img_thumb.php
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Entropy: 6.12 (threshold: 5.5)
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Patterns matched: eval(), base64_decode(), str_rot13()
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Last modified: 2025-12-01 03:42:00 (outside business hours)
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Verdict: SUSPICIOUS - likely obfuscated webshell
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```
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