7. DoS 拒絕服務攻擊

class Rack::Attack

  throttle('req/ip', :limit => 180, :period => 1.minutes) do |req|
    req.ip
  end

  ### Prevent Brute-Force Login Attacks ###

  # The most common brute-force login attack is a brute-force password
  # attack where an attacker simply tries a large number of emails and
  # passwords to see if any credentials match.
  #
  # Another common method of attack is to use a swarm of computers with
  # different IPs to try brute-forcing a password for a specific account.

  # Throttle POST requests to /login by IP address
  #
  # Key: "rack::attack:#{Time.now.to_i/:period}:logins/ip:#{req.ip}"
  throttle('logins/ip', :limit => 5, :period => 20.seconds) do |req|
    if req.path == '/users/sign_in' && req.post?
      req.ip
    end
  end

  # Throttle POST requests to /login by email param
  #
  # Key: "rack::attack:#{Time.now.to_i/:period}:logins/email:#{req.email}"
  #
  # Note: This creates a problem where a malicious user could intentionally
  # throttle logins for another user and force their login requests to be
  # denied, but that's not very common and shouldn't happen to you. (Knock
  # on wood!)
  throttle("logins/email", :limit => 5, :period => 20.seconds) do |req|
    if req.path == '/users/sign_in' && req.post?
      # return the email if present, nil otherwise
      req.params['email'].presence
    end
  end

end