Between 2006 and 2007, there was an almost threefold rise in flaws found in Microsoft software, according to vulnerability-scanning company Qualys.
"We have seen a huge jump in the vulnerabilities in Microsoft Office products," said Amol Sawate, manager of Qualys's vulnerability-management lab. "These charts show growth of nearly 300 percent from 2006 to 2007, primarily in new Excel vulnerabilities that can easily be exploited by getting unsuspecting users to open Excel files sent via email and instant message."
Alan Paller, director of research for the Sans Institute, a computer-security training organisation, said that the reason more vulnerabilities were being found was that it was becoming increasingly profitable for crooks to target the software.
"It isn't that Microsoft isn't doing a better job," Paller said. "The reason [is that] it is so lucrative to find vulnerabilities in Excel and Word, so there are a lot of [hackers] searching for them."
Microsoft could offer no comment at the time of writing.