Attackers have found another hole in Microsoft's Office products. On Thursday, Symantec reported that it has discovered a targeted attack that takes advantage of an unpatched vulnerability in the company’s PowerPoint software.

The hackers behind this attack are using the same techniques that were used in previously reported Word and Excel attacks, said Dave Cole, a director with Symantec Security Response.

"It's similar to the pattern we've seen over the past few months where they're using a previously unknown Microsoft vulnerability, and an e-mail enticement to get a backdoor on someone's machine."

Cole believes that the same hackers may be behind all three attacks. "It looks like it may be the same group just based on the similarly of attacks," he said.

As with the Word and Excel attacks, this latest malware is not widespread.

This PowerPoint attack was discovered late Wednesday by a Symantec customer, who received a Chinese-character e-mail from a Gmail account.

The e-mail contained a PowerPoint attachment that installed two pieces of malicious code when opened: a Trojan horse program, called Trojan.PPDDropper.B, and a backdoor program called Backdoor.Bifrose.E.

The backdoor program tries to cover its tracks, by writing over the original PowerPoint document. It then awaits instructions from the attackers, who can use it to control the infected system.

Office is fast becoming the target of choice for hackers.

Microsoft patched a total of 12 Office vulnerabilities on Tuesday, but the PowerPoint bug used by this latest malware was not one of them, according to Cole.

Microsoft is investigating the vulnerability, said Stephen Toulouse, a security program manager with Microsoft's security response center.

Symantec is studying it as well. The security vendor said it does not yet know if the attack is specific to PowerPoint, or whether it affects all Office products.