An initial signal indicating that Apple's success with iTunes may soon attract hackers has emerged, according to security firm Trend Micro.

A new worm, WORM_OPANKI.Y, is circulating online. It poses as an iTunes file and is spreading using AOL Instant Messenger (AIM). While it does not affect Mac users, it does affect most breeds of the Windows OS.

Beware “exe” files bearing gifts

The worm poses as a file named "iTunes.exe" in an attempt to trick users, "into thinking that this worm is associated with a legitimate product," Trend Micro warns.

However, when activated the worm actually sends a message to all online contacts of an affected user, which reads, "this picture never gets old". Each message has a link to a URL where users download a file that appears to be a JPEG.

Also when activated, the software will begin to download spyware and pop-ups. It also tracks Internet sites infected users visit.

Backdoor worm

Trend Micro also warns: "This worm has backdoor capabilities. It opens a random TCP port and connects to the Internet Relay Chat (IRC) server Once connected, it joins the IRC channel #fate, where it listens for commands from a remote malicious user. It then executes these commands locally on affected machines."

It's not a major threat, according to the security firm. It has not yet spread too widely, the firm adds.