Researchers have uncovered sophisticated attack code circulating on the net that exploits a critical vulnerability in the most recent version of Adobe Reader.

The click-and-get-hacked exploit spreads through email that contains a booby-trapped PDF file that remains virtually undetected by most anti-virus programs, according to Mila Parkour, the security researcher who first alerted Adobe to the threat. It was being sent to a small group of individuals who “work on common issues,” he said, causing him to believe they were narrowly selected by the attackers.

Adobe on Wednesday confirmed that the vulnerability affects Reader 9.3.4 and earlier versions for Windows, Mac OS X, and Unix. The company's security team is in the process of figuring out when it will release a patch. Adobe is working with security companies to help them develop detection and quarantine techniques to contain any attacks.

In the meantime, there are no mitigations users can take other than to exercise due care in opening PDF documents. It may also make sense to use an alternate PDF viewer such as FoxIT, but it's not yet been confirmed that that other programs aren't vulnerable.

The malicious PDF, which also exploits Adobe Acrobat, uses some highly sophisticated techniques to ensure success. It contains three separate font packages so it works on multiple versions of the Adobe programs, and it also has been designed to bypass protections such as ASLR, or address space layout randomization and DEP, and data execution prevention, which are built in to more recent versions of Microsoft Windows.

Engineers with the Metasploit framework are in the process of building a module that will make the exploit work with the open-source program for security professionals and hackers. An update could come as soon as Thursday, H D Moore, CSO of Rapid7 and chief architect of the Metasploit project, told The Register.

“It's a pretty complicated exploit and it's going to take a while to take apart,” he said.

The exploit comes as Adobe is putting the finishing touches on a security feature that's designed to significantly lessen the severity of attacks that exploit buffer overflows and other types of common bugs in Reader. The “sandbox” is intended to put a container around the application so that sensitive parts of the operating system can't be accessed by rogue code. Adobe has said it will be available by the end of this year.

Active exploits are likely to become more widespread once the attack code is put into Metasploit.

For now, white hats and black hats alike can glean further details from this analysis on the Contagio Malware Dump blog. It's maintained by Parkour, who described the project as a hobby. ®