If you just go ahead and copy this to /config/initializers/rack_attack.rb, then you'll be safe from 95% of bad requests. This won't stop sophisticated hackers, but at least you can sleep more soundly knowing that your application isn't going to be accidentally taken down by a misconfigured web scraper in the middle of the night. If this isn't enough for you, check out Advanced Configuration too.
class Rack::Attack
### Configure Cache ###
# If you don't want to use Rails.cache (Rack::Attack's default), then
# configure it here.
#
# Note: The store is only used for throttling (not blocklisting and
# safelisting). It must implement .increment and .write like
# ActiveSupport::Cache::Store
# Rack::Attack.cache.store = ActiveSupport::Cache::MemoryStore.new
### Throttle Spammy Clients ###
# If any single client IP is making tons of requests, then they're
# probably malicious or a poorly-configured scraper. Either way, they
# don't deserve to hog all of the app server's CPU. Cut them off!
#
# Note: If you're serving assets through rack, those requests may be
# counted by rack-attack and this throttle may be activated too
# quickly. If so, enable the condition to exclude them from tracking.
# Throttle all requests by IP (60rpm)
#
# Key: "rack::attack:#{Time.now.to_i/:period}:req/ip:#{req.ip}"
throttle('req/ip', limit: 300, period: 5.minutes) do |req|
req.ip # unless req.path.start_with?('/assets')
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 == '/login' && req.post?
req.ip
end
end
# Throttle POST requests to /login by email param
#
# Key: "rack::attack:#{Time.now.to_i/:period}:logins/email:#{normalized_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 == '/login' && req.post?
# Normalize the email, using the same logic as your authentication process, to
# protect against rate limit bypasses. Return the normalized email if present, nil otherwise.
req.params['email'].to_s.downcase.gsub(/\s+/, "").presence
end
end
### Custom Throttle Response ###
# By default, Rack::Attack returns an HTTP 429 for throttled responses,
# which is just fine.
#
# If you want to return 503 so that the attacker might be fooled into
# believing that they've successfully broken your app (or you just want to
# customize the response), then uncomment these lines.
# self.throttled_response = lambda do |env|
# [ 503, # status
# {}, # headers
# ['']] # body
# end
end