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 last week 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 September 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 warn.
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 by someone using the email 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 known as the "JPEG of Death" exploit, according to Johannes Ullrich, chief technology officer of The SANS Institute's Internet Storm Centre (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 says.
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 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 antivirus 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 email capability that would spread when images are opened, Ullrich said.
As with Sasser and other recent worms that target common Windows components, security experts 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 email 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 could be installed after the Microsoft patch was applied, undoing that patch, Ullrich says.
Currently, most major antivirus software programs can spot corrupted JPEG images. Antivirus software, in combination with the Windows patch, is currently the only known protection from attacks that use the GDI+ vulnerability, he says.