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name: amass description: >- OWASP Amass maps an organization's external attack surface: it finds subdomains, IP addresses, netblocks and ASNs from passive sources and active DNS techniques and stores them in an asset database. Use when: comprehensive subdomain enumeration, attack surface discovery, finding forgotten hosts before a pentest, tracking newly appeared assets, building a graph of target infrastructure. license: Apache-2.0 compatibility: "Linux, macOS or Windows binary, Go 1.26+ to build from source, or Docker" metadata: author: terminal-skills version: "1.1.0" category: research repository: https://github.com/owasp-amass/amass tags: [amass, dns, subdomain, attack-surface, network-mapping] use-cases: - "Enumerate all subdomains for a target domain using passive sources" - "Seed an enumeration with ASNs, CIDR ranges and IP addresses" - "Discover shadow IT and forgotten subdomains before a pentest" - "Build a visual network graph of target infrastructure" agents: [claude-code, openai-codex, gemini-cli, cursor]

OWASP Amass

Overview

OWASP Amass performs attack surface mapping and external asset discovery with open source intelligence and active reconnaissance. This skill covers Amass v5 (v5.1.1 is the latest release checked, April 2026), which is a different tool from v3/v4 in several ways:

• A background engine (REST API on 127.0.0.1:4000) does the work; amass enum starts it automatically if it is not running and talks to it as a client. amass engine runs it by hand.
• enum is passive by default (the -passive flag is deprecated and does nothing). -active adds zone transfer attempts and certificate name grabs.
• Results go to an asset database in the config directory (~/.config/amass on Linux), not to -o/-json files. You read them back with subs, track, viz and assoc.
• The v4 subcommands intel and db and the -json, -o, -asn org lookups of enum/intel are gone. Subcommands now are: enum, subs, track, viz, assoc, engine.

Instructions

Step 1: Install

# Homebrew
brew tap owasp-amass/homebrew-amass && brew install amass

# Go (needs Go 1.26+)
CGO_ENABLED=0 go install -v github.com/owasp-amass/amass/v5/cmd/amass@main

# Release archive, verified against the published checksums
curl -fsSLO https://github.com/owasp-amass/amass/releases/download/v5.1.1/amass_linux_amd64.tar.gz
curl -fsSLO https://github.com/owasp-amass/amass/releases/download/v5.1.1/amass_checksums.txt
sha256sum --ignore-missing -c amass_checksums.txt
tar -xzf amass_linux_amd64.tar.gz

# Docker
docker pull owaspamass/amass:latest
docker run --rm -v ~/.config/amass:/.config/amass owaspamass/amass:latest enum -d northwind-labs.io

amass --version

Release archives exist for linux (amd64, arm64, 386, armv6, armv7), darwin and windows; check the actual file names in the release page before downloading.

Step 2: Passive enumeration (no direct contact with the target)

amass enum -d northwind-labs.io                    # passive is the default
amass enum -d northwind-labs.io,northwind-labs.com # several domains
amass enum -df domains.txt -nocolor -silent        # domains from a file
amass enum -list                                   # list available data sources
amass enum -d northwind-labs.io -include Shodan,VirusTotal -exclude Ahrefs

Step 3: Active enumeration (touches the target's DNS and TLS)

amass enum -active -d northwind-labs.io -p 80,443,8443
amass enum -d northwind-labs.io -brute -w ./subdomains-top1mil-5000.txt
amass enum -d northwind-labs.io -brute -alts -max-depth 3
amass enum -d northwind-labs.io -r 8.8.8.8,1.1.1.1 -timeout 60
amass enum -d northwind-labs.io -rigid           # do not expand scope to related domains

-brute uses a built-in short wordlist unless -w is given. -alts generates altered names (-aw for a custom list). -timeout is minutes without progress before the run stops (default 30).

Step 4: Seed with ASNs, CIDRs and addresses

v5 has no intel command; ranges are scope seeds for enum:

amass enum -asn 64496 -cidr 198.51.100.0/24
amass enum -addr 198.51.100.1-254 -d northwind-labs.io

Finding an organization's ASNs and ranges now has to be done with another source (RIR/RDAP, BGP lookups); Amass also records ASNs and netblocks it meets during enumeration, shown by subs.

Step 5: Read results from the database

amass subs -d northwind-labs.io -names -nocolor            # discovered names only
amass subs -d northwind-labs.io -names -o northwind-names.txt
amass subs -d northwind-labs.io -ip                        # names with addresses
amass subs -d northwind-labs.io -summary                   # ASN table summary
amass subs -d northwind-labs.io -show                      # full results

Step 6: Track new assets over time

amass enum -d northwind-labs.io                            # run again on a schedule
amass track -d northwind-labs.io -since "09/01 00:00:00 2026 UTC"

-since uses the format MM/DD HH:MM:SS YYYY TZ; track lists assets first seen after that moment.

Step 7: Visualize

amass viz -d northwind-labs.io -d3 -dot -gexf -o ./graphs
dot -Tpng ./graphs/amass.dot -o ./graphs/amass.png   # Graphviz, file names may differ

-d3 writes an interactive HTML force graph, -dot a Graphviz file, -gexf a Gephi file. List the output directory to see the exact names.

Step 8: Configure data sources and options

Keys live in ~/.config/amass/datasources.yaml; options in config.yaml (both are created on first run). Pass another file with -config. Keys come from your own accounts; never commit this file.

# ~/.config/amass/datasources.yaml
global_options:
  minimum_ttl: 1440
datasources:
  - name: Shodan
    ttl: 10080
    creds:
      account:
        apikey: REPLACE_WITH_SHODAN_KEY
  - name: VirusTotal
    ttl: 10080
    creds:
      account:
        apikey: REPLACE_WITH_VIRUSTOTAL_KEY
  - name: PassiveTotal
    creds:
      account:
        username: ops@northwind-labs.io
        apikey: REPLACE_WITH_PASSIVETOTAL_KEY

# ~/.config/amass/config.yaml
scope:
  domains:
    - northwind-labs.io
  ports: [80, 443, 8443]
options:
  datasources: "./datasources.yaml"
  bruteforce:
    enabled: false
  alterations:
    enabled: false

The same file can point options.database at Postgres (postgres://…) or Neo4j instead of the default local database.

Examples

Example 1: "Find all subdomains of our domain before the pentest starts"

amass enum -d northwind-labs.io -nocolor -silent
amass subs -d northwind-labs.io -names -o northwind-names.txt
wc -l northwind-names.txt

Result: northwind-names.txt holds one host name per line (for example vpn.northwind-labs.io, staging-api.northwind-labs.io). Resolve them with dnsx or dig before reporting, because some are stale or wildcard answers.

Example 2: "What new hosts appeared since last month?"

amass enum -d northwind-labs.io -nocolor -silent
amass track -d northwind-labs.io -since "09/01 00:00:00 2026 UTC"

Result: a list of names and addresses first discovered after 1 September 2026, the candidates for review.

Guidelines

• Authorization: passive mode still queries third parties, but -active, -brute and -alts send traffic to the target's DNS and web ports. Use them only with written permission.
• Keys matter: without data source keys coverage is limited to free sources such as certificate transparency. Rate limits of free tiers apply.
• Old tutorials are wrong for v5: commands with intel, db, -json, -o on enum, or -d3 -o file.html will fail. Run amass enum -h and amass <subcommand> -h to check flags on your build.
• Runtime: a passive run takes minutes; brute force with large wordlists takes hours. The engine port 4000 must be free.
• Data stays: the asset database keeps history between runs; pass -dir to separate engagements and delete it when the engagement ends.
• Verify discovered names yourself: wildcard DNS and third-party data produce false positives.