The Big Bullseye On Adobe

As the company's software becomes more important to many companies, the attack surface of their products grows.

It's not news that Adobe and their products are a major target of vulnerability research and malicious hackers. This is a trend that will only grow. If they were still doing such things, we could soon expect the Month of Adobe Bugs.

The major security story of a couple weeks ago was initially reported as a zero day, although it turned out that it was effectively patched by the current version. Still, Flash is very widely deployed and is therefore one of the top targets of malicious programmers.

If you believe Adobe's numbers, Flash users update fairly aggressively, especially in the developed world. Perhaps it's still not aggressively enough, as attackers are hot on Adobe's tail.

We learned of a few examples recently from F-Secure. One fairly pedestrian exploit downloads and executes a Trojan Horse program. It's interesting because it uses obfuscation of the shell code, although very simple obfuscation. A more thorough job might have been more difficult to detect.

Of course, Acrobat is also widely-deployed and heavily relied on by large corporations, lawyers, governments, etc., and it is also a major vehicle for real-world attacks, not just empty vulnerability reports. F-Secure reported about a week ago on a malicious PDF they received from VirusTotal. This one is a hoot.

The PDF uses a known vulnerability in Acrobat (they don't say whether the vulnerability is patched, but I suspect not since it triggered on their test system). It drops two files in the .temp folder, an .exe and a second PDF. It runs the .exe and launches the PDF, which appears to be a Department of Homeland Security Form G-235A. The form is a red herring to distract you from the fact that the .exe is a rootkit and reports back through port 80 to malicious servers in China.

How do they make these malicious PDF files? F-Secure stumbled on that as well. The attackers use a tool like GenMDB. You give the tool the PDF you want to trojanize, the .exe you want to embed in it, and the platform on which you want it to run. GenMDB is an odd name; it must have been adapted from a tool to trojanize MDB (Microsoft Access) files, and this version should be GenPDF.

GenMDB raises the whole issue of cross-platform attacks. Since Flash and PDF are cross platform, there have been many vulnerabilities that are cross platform themselves. Since they usually have to execute shell code in order to do something, they end up being platform specific and therefore Windows specific-although I can imagine ways around that. For instance, did you know that PDFs can contain JavaScipt? It might be possible to determine the platform in JavaScript and dispatch the proper exploit code all within the PDF. In any event, F-Secure told me that GenMDB has only one option in the platform listing, XP+Acrobat8.