Hackers are targeting porn news groups with jpeg images that exploit the recently discovered hole in Microsoft software.

The images are the first evidence of public attacks using the critical flaw, which Microsoft identified and patched on 14 September. Users who unwittingly download the poison images could have remote control software installed on their computers that gives remote attackers total control over the machine, experts have warned.

The images have been posted on a variety of news groups where visitors post and share pornographic images, including "alt.binaries.erotica.breasts". Someone using the e-mail address "[email protected]," according to Bugtraq and on Easynews.com, was responsible.

The corrupted images are indistinguishable from other images posted in the group, but contain a slightly modified version of recently released exploit code for the jpeg vulnerability which appeared over the weekend, according to Johannes Ullrich, chief technology officer of The SANS Institute's Internet Storm Center.

Like other exploits for the vulnerability that have appeared in the weeks since Microsoft released its patch, the so-called "Jpeg of Death" uses a jpeg image file formatted to trigger an overflow in a common Windows component called the GDI+ JPEG decoder, which is used by Windows, Internet Explorer, Outlook and many other Windows applications.

When opened by users, the infected JPEGs try to install a copy of Radmin, a legitimate software application that allows users to remotely control their computers. In this case, however, the program is being used by the remote attacker as a Trojan horse program. Infected Windows machines are also programmed to report back to an IRC channel, Ullrich said.

The images only work on Windows XP machines and some of the attack features do not appear to work on all XP machines, Ullrich said. ISC and anti-virus companies cautioned that the newly posted attack images cannot spread and are not, technically, a virus. However, the exploit code could easily be modified to download a virus engine with e-mail capability that would spread when images are opened.

As with Sasser and other recent worms that target common Windows components, security experts worry that the vulnerability could spawn another major worm outbreak. It is remotely exploitable and can be accessed through a long list of popular Windows applications.

Currently, most major anti-virus software programs can spot corrupted jpeg images. Anti-virus software, in combination with the Windows patch, is currently the only known protection from attacks that use the GDI+ vulnerability.