jthack/ffuf_claude_skill/ffuf-skill

Name: ffuf-skill
Author: jthack

Claude Code and agent skill by jthack/ffuf_claude_skill

Trust tier 3

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ext:[{"type":"config","description":"Configuration overrides"}]

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Expert guidance for ffuf web fuzzing during penetration testing, including authenticated fuzzing with raw requests, auto-calibration, and result analysis

Install

npx vskill@latest install jthack/ffuf_claude_skill/ffuf-skill

Semi-extensibleMentions customization, but needs skill-specific knowledge. Read the extensible skills standard

SKILL.md

FFUF (Fuzz Faster U Fool) Skill

Overview

FFUF is a fast web fuzzer written in Go, designed for discovering hidden content, directories, files, subdomains, and testing for vulnerabilities during penetration testing. It's significantly faster than traditional tools like dirb or dirbuster.

Installation

bash

# Using Go
go install github.com/ffuf/ffuf/v2@latest
 
# Using Homebrew (macOS)
brew install ffuf
 
# Binary download
# Download from: https://github.com/ffuf/ffuf/releases/latest

Core Concepts

The FUZZ Keyword

The FUZZ keyword is used as a placeholder that gets replaced with entries from your wordlist. You can place it anywhere:

URLs: https://target.com/FUZZ
Headers: -H "Host: FUZZ"
POST data: -d "username=admin&password=FUZZ"
Multiple locations with custom keywords: -w wordlist.txt:CUSTOM then use CUSTOM instead of FUZZ

Multi-wordlist Modes

clusterbomb: Tests all combinations (default) - cartesian product
pitchfork: Iterates through wordlists in parallel (1-to-1 matching)
sniper: Tests one position at a time (for multiple FUZZ positions)

Common Use Cases

1. Directory and File Discovery

bash

# Basic directory fuzzing
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ
 
# With file extensions
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -e .php,.html,.txt,.pdf
 
# Colored and verbose output
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -c -v
 
# With recursion (finds nested directories)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -recursion -recursion-depth 2

2. Subdomain Enumeration

bash

# Virtual host discovery
ffuf -w /path/to/subdomains.txt -u https://target.com -H "Host: FUZZ.target.com" -fs 4242
 
# Note: -fs 4242 filters out responses of size 4242 (adjust based on default response size)

3. Parameter Fuzzing

bash

# GET parameter names
ffuf -w /path/to/params.txt -u https://target.com/script.php?FUZZ=test_value -fs 4242
 
# GET parameter values
ffuf -w /path/to/values.txt -u https://target.com/script.php?id=FUZZ -fc 401
 
# Multiple parameters
ffuf -w params.txt:PARAM -w values.txt:VAL -u https://target.com/?PARAM=VAL -mode clusterbomb

4. POST Data Fuzzing

bash

# Basic POST fuzzing
ffuf -w /path/to/passwords.txt -X POST -d "username=admin&password=FUZZ" -u https://target.com/login.php -fc 401
 
# JSON POST data
ffuf -w entries.txt -u https://target.com/api -X POST -H "Content-Type: application/json" -d '{"name": "FUZZ", "key": "value"}' -fr "error"
 
# Fuzzing multiple POST fields
ffuf -w users.txt:USER -w passes.txt:PASS -X POST -d "username=USER&password=PASS" -u https://target.com/login -mode pitchfork

5. Header Fuzzing

bash

# Custom headers
ffuf -w /path/to/wordlist.txt -u https://target.com -H "X-Custom-Header: FUZZ"
 
# Multiple headers
ffuf -w /path/to/wordlist.txt -u https://target.com -H "User-Agent: FUZZ" -H "X-Forwarded-For: 127.0.0.1"

Filtering and Matching

Matchers (Include Results)

-mc: Match status codes (default: 200-299,301,302,307,401,403,405,500)
-ml: Match line count
-mr: Match regex
-ms: Match response size
-mt: Match response time (e.g., >100 or <100 milliseconds)
-mw: Match word count

Filters (Exclude Results)

-fc: Filter status codes (e.g., -fc 404,403,401)
-fl: Filter line count
-fr: Filter regex (e.g., -fr "error")
-fs: Filter response size (e.g., -fs 42,4242)
-ft: Filter response time
-fw: Filter word count

Auto-Calibration (USE BY DEFAULT!)

CRITICAL: Always use -ac unless you have a specific reason not to. This is especially important when having Claude analyze results, as it dramatically reduces noise and false positives.

bash

# Auto-calibration - ALWAYS USE THIS
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -ac
 
# Per-host auto-calibration (useful for multiple hosts)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -ach
 
# Custom auto-calibration string (for specific patterns)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -acc "404NotFound"

Why `-ac` is essential:

Automatically detects and filters repetitive false positive responses
Removes noise from dynamic websites with random content
Makes results analysis much easier for both humans and Claude
Prevents thousands of identical 404/403 responses from cluttering output
Adapts to the target's specific behavior

When Claude analyzes your ffuf results, `-ac` is MANDATORY - without it, Claude will waste time sifting through thousands of false positives instead of finding the interesting anomalies.

Rate Limiting and Timing

Rate Control

bash

# Limit to 2 requests per second (stealth mode)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -rate 2
 
# Add delay between requests (0.1 to 2 seconds random)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -p 0.1-2.0
 
# Set number of concurrent threads (default: 40)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -t 10

Time Limits

bash

# Maximum total execution time (60 seconds)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -maxtime 60
 
# Maximum time per job (useful with recursion)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -maxtime-job 60 -recursion

Output Options

Output Formats

bash

# JSON output
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -o results.json
 
# HTML output
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -of html -o results.html
 
# CSV output
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -of csv -o results.csv
 
# All formats
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -of all -o results
 
# Silent mode (no progress, only results)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -s
 
# Pipe to file with tee
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -s | tee results.txt

Advanced Techniques

Using Raw HTTP Requests (Critical for Authenticated Fuzzing)

This is one of the most powerful features of ffuf, especially for authenticated requests with complex headers, cookies, or tokens.

Workflow:

Capture a full authenticated request (from Burp Suite, browser DevTools, etc.)
Save it to a file (e.g., req.txt)
Replace the value you want to fuzz with the FUZZ keyword
Use the --request flag

bash

# From a file containing raw HTTP request
ffuf --request req.txt -w /path/to/wordlist.txt -ac

Example req.txt file:

http

POST /api/v1/users/FUZZ HTTP/1.1
Host: target.com
User-Agent: Mozilla/5.0
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
Cookie: session=abc123xyz; csrftoken=def456
Content-Type: application/json
Content-Length: 27
 
{"action":"view","id":"1"}

Use Cases:

Fuzzing authenticated endpoints with complex auth headers
Testing API endpoints with JWT tokens
Fuzzing with CSRF tokens, session cookies, and custom headers
Testing endpoints that require specific User-Agents or Accept headers
POST/PUT/DELETE requests with authentication

Pro Tips:

You can place FUZZ in multiple locations: URL path, headers, body
Use -request-proto https if needed (default is https)
Always use -ac to filter out authenticated "not found" or error responses
Great for IDOR testing: fuzz user IDs, document IDs, etc. in authenticated contexts

bash

# Common authenticated fuzzing patterns
ffuf --request req.txt -w user_ids.txt -ac -mc 200 -o results.json
 
# With multiple FUZZ positions using custom keywords
ffuf --request req.txt -w endpoints.txt:ENDPOINT -w ids.txt:ID -mode pitchfork -ac

Proxy Usage

bash

# HTTP proxy (useful for Burp Suite)
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -x http://127.0.0.1:8080
 
# SOCKS5 proxy
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -x socks5://127.0.0.1:1080
 
# Replay matched requests through proxy
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -replay-proxy http://127.0.0.1:8080

Cookie and Authentication

bash

# Using cookies
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -b "sessionid=abc123; token=xyz789"
 
# Client certificate authentication
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -cc client.crt -ck client.key

Encoding

bash

# URL encoding
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -enc 'FUZZ:urlencode'
 
# Multiple encodings
ffuf -w /path/to/wordlist.txt -u https://target.com/FUZZ -enc 'FUZZ:urlencode b64encode'

Testing for Vulnerabilities

bash

# SQL injection testing
ffuf -w sqli_payloads.txt -u https://target.com/page.php?id=FUZZ -fs 1234
 
# XSS testing
ffuf -w xss_payloads.txt -u https://target.com/search?q=FUZZ -mr "<script>"
 
# Command injection
ffuf -w cmdi_payloads.txt -u https://target.com/execute?cmd=FUZZ -fr "error"

Batch Processing Multiple Targets

bash

# Process multiple URLs
cat targets.txt | xargs -I@ sh -c 'ffuf -w wordlist.txt -u @/FUZZ -ac'
 
# Loop through multiple targets with results
for url in $(cat targets.txt); do 
    ffuf -w wordlist.txt -u $url/FUZZ -ac -o "results_$(echo $url | md5sum | cut -d' ' -f1).json"
done

Best Practices

1. ALWAYS Use Auto-Calibration

Use -ac by default for every scan. This is non-negotiable for productive pentesting:

bash

ffuf -w wordlist.txt -u https://target.com/FUZZ -ac

2. Use Raw Requests for Authentication

Don't struggle with command-line flags for complex auth. Capture the full request and use --request:

bash

# 1. Capture authenticated request from Burp/DevTools
# 2. Save to req.txt with FUZZ keyword in place
# 3. Run with -ac
ffuf --request req.txt -w wordlist.txt -ac -o results.json

3. Use Appropriate Wordlists

Directory discovery: SecLists Discovery/Web-Content (raft-large-directories.txt, directory-list-2.3-medium.txt)
Subdomains: SecLists Discovery/DNS (subdomains-top1million-5000.txt)
Parameters: SecLists Discovery/Web-Content (burp-parameter-names.txt)
Usernames: SecLists Usernames
Passwords: SecLists Passwords
Source: https://github.com/danielmiessler/SecLists

3. Rate Limiting for Stealth

Use -rate to avoid triggering WAF/IDS or overwhelming the server:

bash

ffuf -w wordlist.txt -u https://target.com/FUZZ -rate 2 -t 10

4. Filter Strategically

Check the default response first to identify common response sizes, status codes, or patterns
Use -fs to filter by size or -fc to filter by status code
Combine filters: -fc 403,404 -fs 1234

5. Save Results Appropriately

Always save results to a file for later analysis:

bash

ffuf -w wordlist.txt -u https://target.com/FUZZ -o results.json -of json

6. Use Interactive Mode

Press ENTER during execution to drop into interactive mode where you can:

Adjust filters on the fly
Save current results
Restart the scan
Manage the queue

7. Recursion Depth

Be careful with recursion depth to avoid getting stuck in infinite loops or overwhelming the server:

bash

ffuf -w wordlist.txt -u https://target.com/FUZZ -recursion -recursion-depth 2 -maxtime-job 120

Common Patterns and One-Liners

Quick Directory Scan

bash

ffuf -w ~/wordlists/common.txt -u https://target.com/FUZZ -mc 200,301,302,403 -ac -c -v

Comprehensive Scan with Extensions

bash

ffuf -w ~/wordlists/raft-large-directories.txt -u https://target.com/FUZZ -e .php,.html,.txt,.bak,.old -ac -c -v -o results.json

Authenticated Fuzzing (Raw Request)

bash

# 1. Save your authenticated request to req.txt with FUZZ keyword
# 2. Run:
ffuf --request req.txt -w ~/wordlists/api-endpoints.txt -ac -o results.json -of json

API Endpoint Discovery

bash

ffuf -w ~/wordlists/api-endpoints.txt -u https://api.target.com/v1/FUZZ -H "Authorization: Bearer TOKEN" -mc 200,201 -ac -c

This is the start of the file. Read the full SKILL.md on GitHub.

Security

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Source

SKILL.md in the repositoryCheckingffuf-skill/SKILL.md

Popularity

Repository stars: 127
Repository forks: 7
7-day trend score: 24

Stars and forks are for the whole GitHub repository, not this skill alone. Refreshed 21 Mar 2026, 7 months ago.

Extension points

configConfiguration overrides

Learn the extensible skills standard

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