The Gumblar malware, which returned in the past several weeks, appears to be neutralized for the moment. In its return, Gumblar was using compromised websites to host its malware code instead of a website owned by the person(s) behind the hack. Other websites that have been compromised by Gumblar, then have code inserted into them that causes a file, with the malware code, to be loaded from one the websites that host the malware.
The code on those websites hosting the malware has now been changed from the malware infection code to Javascript that neutralizes iframes and a message that reads “iframes are EVIL! Hate Zeus!”. If the iframe neutralizing code is loaded on a website that contains other malware scripts, which occurs in some cases, it could possibly disable those scripts.
Gumblar inserted backdoor scripts as part of its hack, which someone other than the original hacker could have used to change the code stored on the host websites. It is also possible that the originally hacker made the change for some unknown reason.