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Gem Version Coverage Status

A SSH configuration and policy scanner

⚠️ Deprecation Notice ⚠️

Mozilla is no longer maintaining the SSH Scan project.

Please fork it to continue development.

Key Benefits

  • Minimal Dependencies - Uses native Ruby and BinData to do its work, no heavy dependencies.
  • Not Just a Script - Implementation is portable for use in another project or for automation of tasks.
  • Simple - Just point ssh_scan at an SSH service and get a JSON report of what it supports and its policy status.
  • Configurable - Make your own custom policies that fit your unique policy requirements.


To install and run as a gem, type:

gem install ssh_scan

To run from a docker container, type:

docker pull mozilla/ssh_scan
docker run -it mozilla/ssh_scan -t

To install and run from source, type:

# clone repo
git clone
cd ssh_scan

gem install bundler
bundle install


Example Command-Line Usage

Run ssh_scan -h to get this

ssh_scan v0.0.21 (

Usage: ssh_scan [options]
    -t, --target [IP/Range/Hostname] IP/Ranges/Hostname to scan
    -f, --file [FilePath]            File Path of the file containing IP/Range/Hostnames to scan
    -T, --timeout [seconds]          Timeout per connect after which ssh_scan gives up on the host
    -L, --logger [Log File Path]     Enable logger
    -O, --from_json [FilePath]       File to read JSON output from
    -o, --output [FilePath]          File to write JSON output to
    -p, --port [PORT]                Port (Default: 22)
    -P, --policy [FILE]              Custom policy file (Default: Mozilla Modern)
        --threads [NUMBER]           Number of worker threads (Default: 5)
        --fingerprint-db [FILE]      File location of fingerprint database (Default: ./fingerprints.db)
        --suppress-update-status     Do not check for updates
    -u, --unit-test [FILE]           Throw appropriate exit codes based on compliance status
    -v, --version                    Display just version info
    -h, --help                       Show this message


  ssh_scan -t
  ssh_scan -t
  ssh_scan -t ::1
  ssh_scan -t ::1 -T 5
  ssh_scan -f hosts.txt
  ssh_scan -o output.json
  ssh_scan -O output.json -o rescan_output.json
  ssh_scan -t -p 22222
  ssh_scan -t -p 22222 -L output.log -V INFO
  ssh_scan -t -P custom_policy.yml
  ssh_scan -t --unit-test -P custom_policy.yml

ssh_scan as a service/api?

This project is solely for ssh_scan engine/command-line usage.

If you would like to run ssh_scan as a service, please refer to the ssh_scan_api project

Rubies Supported

This project is integrated with travis-ci and is regularly tested to work with multiple rubies.

To checkout the current build status for these rubies, click here.


If you are interested in contributing to this project, please see


Sources of Inspiration for ssh_scan

  • Mozilla OpenSSH Security Guide - For providing a sane baseline policy recommendation for SSH configuration parameters (eg. Ciphers, MACs, and KexAlgos).