New attacks exploit vuln in (fully-patched) Adobe Flash

Online criminals are targeting a previously unknown vulnerability in the latest versions of Adobe's ubiquitous Flash Player that allows them to take complete control of end users' computers, security researchers warn.

Although the exploit can be triggered using malicious PDF files opened by Adobe's Reader application, a more common technique uses a 1.1 kilobyte Adobe Flash file to target the vulnerability, says Paul Royal, principal researcher for Purewire, a company that protects web users against malicious sites. At the moment, the number of attacks is small, but that's likely to change.

"So far, I've seen just a handful of websites offering this zero-day exploit, although the number will obviously increase the minute that a public proof of concept version of the weaponized vulnerability gets published," Royal tells The Register. "Once this thing hits Milw0rm you'll see thousands of sites."

Adding to the urgency, none of the major anti-virus engines were detecting the poisoned SWF files at time of writing. What's more, some of the sites serving the malicious, one-frame movie are legitimate websites that have been compromised, making it difficult for people to protect themselves against the attack.

A less common attack involves the use of booby-trapped PDF documents, which when opened triggers the Flash vulnerability, both Purewire and Symantec say. As we've counseled before, this method can be blocked by preventing Adobe Reader from running javascript, but users should remember this does nothing to prevent them from being compromised by the malicious SWF files.

The attacks come two months after Adobe vowed to beef up the security of its Reader and Acrobat document applications by subjecting them to more rigorous testing and a more predictable schedule of patching. While the initiative was a good start, the latest exploits show the shortsightedness of not applying the same regimen to Flash Player, which runs on the vast majority of the world's computers, including those running Windows, Mac OS X, and Linux.

Judging from this bug report on Adobe's own website, the flaw behind the the Flash exploit was reported in December, Royal says. While the bug is reported to trigger only a crash, the report said it was reproducible "every time."

An analysis of the PDF exploit suggests the source code was compiled on July 9, suggesting the attacks have been in circulation for a few weeks.

On Wednesday, Adobe's product security response team issued a two-sentence advisory saying it is investigating reports of a vulnerability affecting the latest versions of both its Reader and Flash applications. Information about work-arounds or when a fix might be available wasn't included.

According to this VirusTotal analysis, none of the top 41 anti-virus providers were able to detect the malicious SWF files at time of writing. A separate VirusTotal analysis shows seven AV companies detecting the PDF exploit, and Symantec says it also detects the vulnerability as Trojan.Pidief.G .

As always, the threat can be mitigated by using Firefox with plugins such as NoScript. Of course, all bets are off if one of your trusted sites happens to get compromised by one of the attackers, so users shouldn't considered this protection foolproof.

More about this vulnerability from Sans and Symantec is available here and here. ®

Update

In an advisory that was updated after this article was published, Adobe says the "vulnerability exists in the current versions of Flash Player (v9.0.159.0 and v10.0.22.87) for Windows, Macintosh and Linux operating systems, and the authplay.dll component that ships with Adobe Reader and Acrobat v9.x for Windows, Macintosh and UNIX operating systems."

The company expects to release an update fixing Flash in Windows, OS X and Unix on July 30 and fixing Acrobat and Reader on those same three platforms on July 31.

CERT recommends here that Windows users disable Flash in Reader by renaming the authplay.dll and rt3d.dll files.

Security firm FireEye provides two excellent deep dives into the attack and the malware here and here.