Apparently there is no honor among thieves and hackers. Some of you may remember that after the site Megaupload was taken down, the hacker group Anonymous decided to attack other websites, such as the US. Department of Justice, in retaliation. To hit the sites even harder, instructions and software for joining in the distributed denial-of-service (DDoS) attacks were posted online. Well, it turns whichever Anonymous member posted the information was interested in hurting more than the DoJ.
Zeus is a piece of malware meant to enslave its host computer and steal data, and was contained in the Slowloris DDoS software. According to Symantec, the computers in the voluntary Anonymous botnet were compromised, and information, such as banking details, was sent to someone.
I am not sure if "ironic" is descriptive enough.