Malicious hackers are seeding Internet news groups that traffic in pornography with JPEG images that take advantage of a recently disclosed security hole in Microsoft's software, according to warnings from anti-virus software companies and Internet security groups.

The reports are the first evidence of public attacks using the critical flaw, which Microsoft identified and patched on Sept. 14. 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 warned.

The images were posted in a variety of Internet news groups where visitors post and share pornographic images or "binaries." The altered JPEG images were posted to groups such as "alt.binaries.erotica.breasts" on Monday by someone using the e-mail address "Power-Poster@power-post.org," according to information published on the online security discussion group Bugtraq and on Easynews.com, a Web portal for Usenet, the global network of news servers.

The corrupted JPEG 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 called the "JPEG of Death" exploit, which appeared over the weekend, according to Johannes Ullrich, CTO of The SANS Institute's Internet Storm Center (ISC).

Like other exploits for the vulnerability that have appeared in the weeks since Microsoft released its patch, the JPEG of Death uses a JPEG 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, Ullrich said.

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 Internet relay chat (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, Ullrich said.

The IDG News Service is a Network World affiliate.

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