New Adobe Attack Using Stolen Certificates

As Adobe yesterday warned users of new attacks against Reader and Acrobat exploiting a previously unknown flaw in its software, researchers spotted a targeted assault that deployed stolen certificates as well a new spin on an old exploit method.

Adobe issued an advisory yesterday about attacks in the wild exploiting a new bug the software firm had just learned of the day before. The critical flaw affects Adobe Reader 9.3.4 and earlier for Windows, Macintosh, and Unix, and Acrobat 9.3.4 for Windows and Mac. The flaw could let an attacker crash the application and take control over the victim's machine. But so far, no workarounds and no patch.

Adobe didn't provide details on the nature of the flaw, but Secunia says it's a font-parsing buffer overflow vulnerability.

"Adobe is in the process of evaluating the schedule for an update to resolve this vulnerability," Adobe said in its advisory. "Unfortunately, there are no mitigations we can offer. However, Adobe is actively sharing information about this vulnerability (and vulnerabilities in general) with partners in the security community to enable them to quickly develop detection and quarantine methods to protect users until a patch is available."

Meanwhile, Roel Schouwenberg, senior antivirus researcher for Kaspersky Lab, studied an attack exploiting the flaw that uses a stolen digital certificate from a credit union to sign the infected PDF file -- akin to what the Stuxnet attacks did. Schouwenberg says as this technique takes off, it will result in more missed attacks as well as more false positives from security software. "I predict that the security industry will have more misses of these files that come with stolen signatures, or [have] more false positives. We could well be in this high false positives [trend] next year, which we haven't seen in a while," he says.

While the exploit itself is fairly simple, the attack also uses return-oriented programming, or ROP, where it uses existing code already in the machine's memory rather than injecting new code into memory and trying to execute it, Schouwenberg says. It sneaks by Microsoft's Data Execution Protection (DEP) and Address Space Layout Randomization (ASLR), he says.

ROP could be the next big thing in exploits, he says. It basically works like this: "ROP may actually start in the memory of one process, and start executing in one memory space and string together existing pieces of code and use it for the exploit," he says. This is ideal for evading Microsoft's DEP and ASLR, and possibly similar techniques that are designed to stop the introduction of new code into the victim's machine, Schouwenberg says.

"They have no method of combating already existing code that's being used in a different way," he says.

The attack also demonstrates how the bad guys are looking for ways to exploit Windows 7 machines. "Most Adobe exploits do not function in Windows 7. So in this case, the attackers obviously took the time to make sure the code [worked] with the latest technology," Schouwenberg says.

Kaspersky's Schouwenberg says at first he thought the email message -- which had a subject line having to do with improving your golf swing -- was just some run-of-the-mill spam until he found the exploit in the PDF. "It looks to be somewhat of a targeted attack," he says, possibly going after executive types who like to play golf.

His analysis and screen shots of the attack are here.

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