Hackers are exploiting a known and patched vulnerability in coding language Ruby on Rails. The exploit that is currently being used by attackers adds a custom cron job (a scheduled task on Linux machines) that executes a sequence of commands. The resulting malware is a bot that connects to an IRC (Internet Relay Chat) server and joins a predefined channel where it waits for commands from the attackers. The original flaw, announced in CVE-2013-0156, is located in the Ruby on.
Source: https://thehackernews.com/2013/05/ruby-on-rails-exploit-could-hijack.html