Ruby on Rails

How Beam reads a Rails app

There's no in-process SDK for this stack, so the app writes what Beam needs to its logs and beam monitor reads them on the same server or container. Only redacted findings leave it. Two kinds of line:

One JSON line per request, with method, path (with the query string), status, ip, user_agent, host and duration_ms. The status is what lets Beam tell an attack your app refused from one it answered.
Security events as plain lines, worded like this (Beam matches the wording and reads user= and ip=):

login failed user=42 ip=203.0.113.7
login succeeded user=42 ip=203.0.113.7
granted admin role to user=99 by user=12
API key created user=12
{"event":"llm_usage","user":"42","model":"gpt-5","total_tokens":1834}

Use an opaque user id, never an email. New outbound hosts are only reported by the Node.js SDK; for this stack, restrict outbound traffic at the network instead.

Before you start

Do steps 1 and 2 of the general cookbook first: App monitoring is on, the app is added, and its beam_app_ token is in your secret store as BEAM_APP_TOKEN. Everything below needs @agent-beam/beam 0.2.32 or newer.

Log each request with its status

# lib/beam_request_log.rb
require "json"
require "logger"

class BeamRequestLog
  LOG = Logger.new("/var/log/app/requests.log", formatter: ->(*, msg) { "#{msg}\n" })

  def initialize(app) = @app = app

  def call(env)
    started = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    status, headers, body = @app.call(env)
    request = ActionDispatch::Request.new(env)
    LOG.info(JSON.generate(
      method: request.request_method,
      path: request.fullpath,
      status: status,
      ip: request.remote_ip,
      user_agent: request.user_agent.to_s,
      host: request.host,
      duration_ms: ((Process.clock_gettime(Process::CLOCK_MONOTONIC) - started) * 1000).round,
    ))
    [status, headers, body]
  end
end

# config/application.rb
require_relative "../lib/beam_request_log"
config.middleware.insert_before 0, BeamRequestLog

request.remote_ip honors your trusted proxies (config.action_dispatch.trusted_proxies).

Log sign-ins, admins and keys

With Devise (Warden):

# config/initializers/beam_security.rb
BEAM_SECURITY = Logger.new("/var/log/app/security.log", formatter: ->(*, msg) { "#{msg}\n" })

Warden::Manager.after_authentication do |user, auth, _opts|
  BEAM_SECURITY.info("login succeeded user=#{user.id} ip=#{auth.request.remote_ip}")
end

Warden::Manager.before_failure do |env, _opts|
  request = ActionDispatch::Request.new(env)
  user_id = User.find_by(email: request.params.dig("user", "email"))&.id
  BEAM_SECURITY.warn("login failed user=#{user_id} ip=#{request.remote_ip}")
end

Where you grant admin rights or issue keys:

BEAM_SECURITY.info("granted admin role to user=#{target.id} by user=#{current_user.id}")
BEAM_SECURITY.info("API key created user=#{current_user.id}")
BEAM_SECURITY.info({ event: "llm_usage", user: current_user.id.to_s, model: model, total_tokens: usage["total_tokens"] }.to_json)

Run `beam monitor` next to the app

npm install -g @agent-beam/beam
beam monitor --stack rails --file /var/log/app/requests.log --file /var/log/app/security.log --app /srv/app

--stack rails turns on this framework's rules and rolls up attacks on frameworks you don't run; --app also checks the app's lockfiles daily (and would detect the stack on its own). Keep it running with systemd:

# /etc/systemd/system/beam-monitor.service
[Unit]
Description=AgentBeam App monitoring
After=network-online.target

[Service]
EnvironmentFile=/etc/beam/app.env
ExecStart=/usr/bin/env beam monitor --stack rails --file /var/log/app/requests.log --file /var/log/app/security.log --app /srv/app
Restart=always
User=beam

[Install]
WantedBy=multi-user.target

sudo install -m 600 /dev/null /etc/beam/app.env && echo "BEAM_APP_TOKEN=beam_app_..." | sudo tee /etc/beam/app.env >/dev/null
sudo systemctl daemon-reload && sudo systemctl enable --now beam-monitor

In Docker or Kubernetes, run the same command in a sidecar that mounts the log directory read-only, with BEAM_APP_TOKEN from a secret.

Prove it works

beam monitor status   # app, level, stack, usage
beam monitor test     # a test finding through your alert workflows
curl -s "https://your-app.example.com/?id=1%20UNION%20SELECT%201" -o /dev/null

Within a minute, the SQL injection test shows on App monitoring: under Needs action if the app answered 2xx, or counted under "needed nothing from you" if it refused it. Then sign in to a test account with a wrong password ten times and the right one once: Sign-in succeeded after 10 failed attempts appears as critical.

Check dependencies on every pull request

# .github/workflows/beam-cve.yml
name: Dependency check
on: [pull_request]
jobs:
  cve:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npx -y @agent-beam/beam cve check . --fail-on high
        env:
          BEAM_APP_TOKEN: ${{ secrets.BEAM_APP_TOKEN }}

Gemfile.lock is checked.

What Beam watches for on this stack

Besides every built-in rule and the attack-in-progress signals:

Rule	Means	Severity
Rails info pages served publicly	`/rails/info/properties` or `/rails/info/routes` answered 2xx (development-only pages)	High
Template injection	ERB-style `<%= 7*7 %>` payloads	High

Attacks on other frameworks (WordPress probes, Laravel or Spring exploits, and so on) are rolled up as Not your stack when there's no status to say otherwise, and never alert.

Close what Beam would catch

Beam raises these when they're found; better that there's nothing to find:

Run production with RAILS_ENV=production; /rails/info must never answer there.
Keep config.consider_all_requests_local = false in production.
Rate-limit sign-ins (Rack::Attack) and enable Devise's lockable.

Coverage checklist

Feature	Done when
Request log with status	Findings show Answered, Refused or Errored
Stack declared	`beam monitor` prints the stack at start
Sign-in events	`login failed` and `login succeeded` lines are written
Admin and key events	Role grants and new keys are logged
LLM spend	An `llm_usage` line follows each model call
Dependency checks	The CI job runs on pull requests
Alerts	Critical pages someone, high reaches a channel (step 8)
Routine	Someone reads Needs action daily and Attack analytics weekly