Hackers use porn to target Microsoft JPEG flaw

The malicious code is being called the 'JPEG of Death' exploit

Malicious hackers are seeding Internet newsgroups that traffic in pornography with JPEG images that take advantage of a recently disclosed security hole in Microsoft Corp.'s software, according to warnings from antivirus 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 (see story). Users who unwittingly download the poison images could have software installed on their computers that gives remote attackers total control over the machine, experts said.

The images were posted in a variety of Internet newsgroups where visitors post and share pornographic images, or "binaries." The altered JPEG images were posted to groups such as "alt.binaries.erotica.breasts" yesterday by someone using the e-mail address "Power-Poster@power-post.org," according to the online security discussion group BugTraq and information posted 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, said Johannes Ullrich, chief technology officer of the SANS Institute's Internet Storm Center (ISC). The ISC has also posted information about the exploit online.

Like other exploits for the vulnerability that have appeared 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. That decoder 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 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 channel, Ullrich said.

The images work only on computers running Windows XP, although some of the attack features don't appear to work on all machines running that operating system, Ullrich said.

The ISC and antivirus companies cautioned that the newly posted attack images can't spread and aren't, 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.

As with Sasser and other recent worms that target common Windows components, security experts said they worry that the JPEG vulnerability in GDI+ could spawn another major worm outbreak. The vulnerability is remotely exploitable and can be accessed through a long list of popular Windows applications, including Internet Explorer, the Outlook e-mail program and Microsoft's Office applications.

In addition to GDI+ being a standard component of Windows, different Windows applications frequently distribute their own versions of GDI+. Those versions might reside in folders used by the applications and be out of reach of the Windows patch, or they could be installed after the Microsoft patch was applied, undoing that patch, Ullrich said.

Currently, most major antivirus software programs can spot corrupted JPEG images. Ullrich added that antivirus software, in combination with the Windows patch, is the only known protection from attacks that use the GDI+ vulnerability.

Copyright © 2004 IDG Communications, Inc.

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