Find unused security groups

unused-security-groups.rb

#!/usr/bin/env ruby
 
require 'aws-sdk'
 
ec2 = AWS::EC2.new
elb = AWS::ELB.new
rds = AWS::RDS.new.client # shrug
 
security_groups = ec2.security_groups.map { |sg| sg.id }.sort
instance_sgs = ec2.instances.map { |i| i.security_groups.map { |sg| sg.id } }.flatten.sort
elb_sgs = elb.load_balancers.map { |elb| elb.security_groups.map { |sg| sg.id } }.flatten.sort
rds_sgs = rds.describe_db_instances.db_instances.map { |db| db.vpc_security_groups.map { |sg| sg.vpc_security_group_id } }.flatten.sort
 
puts security_groups - instance_sgs - elb_sgs - rds_sgs