Microsoft's software security team has said it is examining a new flaw in Word but has said it is uncertain when it will be able to release a patch for it.

"Let me reassure everyone that the flaw is absolutely under investigation and we will release a patch or update as soon as we can," said Bruce Cowper, senior program manager at Microsoft Canada.

Microsoft normally releases updates and fixes on the second Tuesday of every month. But occasionally it will release a patch outside the schedule if the hole is significant. The Word hole certainly appears to be that serious in that it enables a hacker to take control of a victim's computer with relative ease.

Microsoft's refusal to state when it will have a patch ready has worried some observers however. "This means the vulnerability could remain open for a month, or until the next periodic update comes," said David Frazer, director of technology services at F-Secure.

Early last week, reports emerged that Microsoft Word programs sold from 2000 to 2006 contained a flaw that enabled hackers to attack a person's computer by sending the victim an email with a Word document attachment containing a virus or malicious code.

The report closely followed news that hackers have released a file that circumvents the much vaunted security feature of Microsoft's recently released operating system Windows Vista.

Cowper said Microsoft's probe could take several days because of a rigorous verification process. The work involves verification of the reported flaw, location of the areas affected by the flaw, and development and testing of a patch.

The new flaw might appear no more dangerous than previously disclosed flaws on Microsoft software, but its potential for damage is exacerbated by Word's popularity, according to one Canadian analyst. "The situation becomes problematic because Word is such a ubiquitous program," said James Quin, senior research analyst for Info-Tech Research.

Because people are so familiar with the program, Quin said, they are less likely to question the origins of an email containing a Word attachment.

Software vulnerabilities have created a thriving market for tech-savvy crooks that search for flaws and auction off this information to the highest bidder.

Until a patch is released the only thing computer users can do is to make sure their anti-virus software are updated and be wary about opening any unsolicited or suspicious e-mail.

Frazer of F-Secure said his firm has identified at least two Trojan viruses that are capable of exploiting Word's latest vulnerability. One of the threats comes from the "cryptic" family of viruses that are able to deploy a malicious code by opening a backdoor entrance into a computer.

The other virus comes from a type called "tiny". These viruses are able to surreptitiously connect a victim's computer to website that can upload malware into the victim's computer, said Frazer. So far, Quin has not heard of any reports of this most recent flaw being exploited by malicious hackers, but he said it also possible that organizations that have been attacked are being "tight lipped" to prevent any negative publicity.