Microsoft has confirmed that hackers are using an unpatched flaw in PowerPoint to assault vulnerable systems.
The attacks rely on tricking prospective marks into opening a maliciously crafted PowerPoint file, either hosted on a website or sent via email. In both scenarios users would have to open a booby-trapped PowerPoint designed to exploit the vulnerability.
In a statement published on Thursday, Microsoft said it was "aware only of limited and targeted attacks that attempt to use this vulnerability".
However, net security firm McAfee said it has "discovered multiple attacks in the field using the PowerPoint exploit" to install Trojans onto vulnerable systems. Hackers have crafted these exploits in an attempt to disguise malign actions, it adds.
"Some of these specially crafted exploits arrived as PowerPoint Showfiles with the '.pps' extension," McAfee reports. "Such files typically open in full screen mode and hide the applications running on the desktop, such as system monitoring tools that could give any clue to the dodgy installation of Trojans to the victim."
Affected software packages include fully patched versions of Microsoft Office PowerPoint 2000, PowerPoint 2002, PowerPoint 2003 and Microsoft Office 2004 for Mac. Other versions including Microsoft Office PowerPoint 2007 and Microsoft Office 2008 for Mac are in the clear.
Microsoft said it was investigating the problem, something that normally results in a patch. The next scheduled Patch Tuesday falls on 14 April, but the necessary update may or may not be ready in time. Microsoft has to find time to develop and test a patch, the particular technical difficulty of which remains unclear and perhaps unknowable outside Redmond.
Microsoft, reasonably enough, routinely holds back details of flaws until patches become available.
An unpatched Excel flaw, which is also the subject of targeted attacks since late February, failed to appear in Microsoft's March patch batch. On other occasions Microsoft has released out-of-band fixes days after a flaw was first exploited.
If we were running bets on security patch availability, then a May fix for both might be the most likely outcome, but this is pure guesswork on our part. The idea that attacks are not hugely widespread is not particularly comforting, because targeted Trojan attacks against government and big business have been a huge problem for at least three or four years. Unpatched Office vulnerabilities are often the weapon of choice in this sort of malfeasance. ®