implementing-attack-surface-management

name	implementing-attack-surface-management
description	Implements external attack surface management (EASM) using Shodan, Censys, and ProjectDiscovery tools (subfinder, httpx, nuclei) for asset discovery, subdomain enumeration, service fingerprinting, and exposure scoring. Includes a weighted risk scoring algorithm based on OWASP attack surface analysis methodology and the Relative Attack Surface Quotient (RSQ). Use when building continuous ASM programs or performing external reconnaissance for security assessments.
domain	cybersecurity
subdomain	offensive-security
tags	["attack-surface","reconnaissance","shodan","censys","subfinder","nuclei","asset-discovery"]
version	1.0
author	mukul975
license	Apache-2.0
nist_csf	["ID.RA-01","GV.OV-02","DE.AE-07"]
mitre_attack	["T1078","T1190","T1059","T1595","T1592"]
source	https://github.com/mukul975/Anthropic-Cybersecurity-Skills
source_commit	04450304b12645cb2b974ab96d28c0664758a88d

Implementing Attack Surface Management

When to Use

• When building an external attack surface management (EASM) program from scratch
• When performing authorized external reconnaissance for penetration testing engagements
• When continuously monitoring organizational exposure across internet-facing assets
• When scoring and prioritizing external attack surface risks for remediation
• When integrating multiple discovery tools into an automated ASM pipeline

Prerequisites

• Python 3.8+ with requests, shodan, censys libraries installed
• Shodan API key (free tier provides 100 queries/month)
• Censys API ID and Secret (free tier available)
• ProjectDiscovery tools installed: subfinder, httpx, nuclei
• Go 1.21+ for building ProjectDiscovery tools from source
• Appropriate authorization for all external scanning activities
• Target domains and IP ranges with written scope documentation

Instructions

Phase 1: Subdomain Enumeration with Multiple Sources

Use subfinder for passive subdomain discovery leveraging dozens of data sources including certificate transparency logs, DNS datasets, and search engines.

# Install ProjectDiscovery tools
go install -v github.com/projectdiscovery/subfinder/v2/cmd/subfinder@latest
go install -v github.com/projectdiscovery/httpx/cmd/httpx@latest
go install -v github.com/projectdiscovery/nuclei/v3/cmd/nuclei@latest

# Basic subdomain enumeration
subfinder -d example.com -o subdomains.txt

# Verbose with all sources and recursive enumeration
subfinder -d example.com -all -recursive -o subdomains_full.txt

# Multi-domain enumeration from file
subfinder -dL domains.txt -o all_subdomains.txt

# Using OWASP Amass for deeper enumeration
amass enum -d example.com -passive -o amass_subdomains.txt

# Merge and deduplicate results
cat subdomains.txt amass_subdomains.txt | sort -u > combined_subdomains.txt

Phase 2: Live Host Discovery and Service Fingerprinting

Probe discovered subdomains to identify live hosts, technologies, and services.

# HTTP probing with technology detection
cat combined_subdomains.txt | httpx -sc -cl -ct -title -tech-detect \
    -follow-redirects -json -o httpx_results.json

# Detailed service fingerprinting
 combined_subdomains.txt | httpx -sc -cl -ct -title -tech-detect \
    -favicon - sha256 -jarm -cdn -cname \
    -follow-redirects -json -o httpx_detailed.json