Microsoft's PowerPoint application is being used in a new attack that exploits an unpatched vulnerability in the popular Office app. The software giant yesterday issued a security alert confirming "limited and targeted attacks" were under way using malicious PowerPoint files that exploit the flaw.

The exploits carry a Trojan, according to Microsoft, and in an interesting twist, the exploit files were recently submitted to the VirusTotal free malware-scanning site. "Either the miscreants who created these exploits were looking to see how antivirus products detect their new files, or the victims were looking to get some information about their maliciousness," blogged Cristian Craioveanu and Ziv Mador of Microsoft's Malware Protection Center.

When exploited, the vulnerability can give an attacker local rights to a user's machine if he opens the malicious PowerPoint file, which is currently being delivered via targeted email messages, but can also be pushed via a Website or instant messaging link.

The vulnerability affects PowerPoint 2000 Service Pack 3, PowerPoint 2002 Service Pack 3, PowerPoint 2003 Service Pack 3, and Microsoft Office 2004 for Mac . The newer Microsoft Office PowerPoint 2007 and Microsoft Office for Mac 2008 are immune.

"Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs," said Bill Sisk, security response communications manager for Microsoft, in a statement.

Paul Henry, security and forensic analyst for Lumension Security, blogged today that the attack is a reminder of the importance of least-privilege user rights. "...A reduced level of privilege for our users can afford significant risk mitigation in the current malware-ridden environment that exists. Simply put, you are not only limiting the users' rights, you are potentially limiting the rights of malware that may infect the users' PC," Henry said.

For now, Microsoft has provided a few workarounds for users to protect against the new PowerPoint attack:

Graham Cluley, senior technology consultant for Sophos, says it's unclear whether Microsoft will have a fix ready in time for its April 14 patch update. "So take action now," he says in his new blog for Dark Reading. "Make sure your antivirus software is configured to automatically update as security vendors are rushing out detection routines, and ensure that your staff knows not to open unsolicited or unknown PowerPoint files, just in case they are carrying a dangerous payload."

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