Microsoft has a new bug to worry about, this time in PowerPoint.

Attackers have been exploiting a newly discovered hole in the presentation software, McAfee has reported.

Researchers were made aware of the attacks when a customer submitted two different malicious PowerPoint files, both of which exploited the same vulnerability, said McAfee's Craig Schmugar. Both files installed malicious remote access Trojan software that then attempted to connect to an outside web server, he said.

Though McAfee is not releasing technical details of the exploit, the security vendor says that it has confirmed that the attack works on three versions of Office running on the Windows 2000 operating system: Office 2000, Office XP, and Office 2003. Other platforms and other Office applications may also be affected, but McAfee has not yet had time to complete its testing, Schmugar has blogged.

Microsoft "has concluded that this issue affects users of Microsoft Office 2000, Microsoft Office 2003, and Microsoft Office XP," the company said. Microsoft and other security vendors, including Symantec, have added signatures to their security products to detect the code.

Over the past few months, attackers have focused on Office, exploiting a number of undisclosed Office bugs in targeted attacks, often on government agencies or contractors. These attacks usually take the form of an email that has a malicious Office document attached and is sent to a small number of target victims.

This latest PowerPoint attack fits that pattern and was sent to a defence contractor, Schmugar said. He declined to provide further details on the intended victim. Because the attack has been extremely limited in scope it is considered to be a low risk for most users, Schmugar said.

News of the attack comes the day after Microsoft issued an emergency patch for a widely exploited bug that affected the VML rendering engine used by Internet Explorer and Outlook. Hackers are exploiting this critical flaw in the browser via mass email and on thousands of websites, security experts said.