The developers of the open source IRC server UnrealIRCd have had to report that the file servers of the project were compromised several months ago and the IRC servers code, Unreal3.2.8.1.tar.gz, was replaced by a version with a backdoor. The backdoor allows anyone to execute commands on the server running Unreal IRCd. Read the full article in this article by The H Security at http://www.hackssecsec.com/unrealIRCd.
Source: https://threatpost.com/irc-server-backdoor-went-unnoticed-7-months-061410/74101/