Windows Vista could be less stable than XP, and prey to a whole new set of security issues, a report from Symantec has suggested.

With the operating system still in beta - and not due to ship until January 2007 at the earliest - Symantec’s researchers examined the part of the software that handled networking in build 5270 of the software. They concluded that since large parts of Vista had been rewritten from scratch, it had introduced a new set of problems.

"Microsoft has removed a large body of tried and tested code and replaced it with freshly written code, complete with new corner cases and defects," CNet News reported the company as saying in Windows Vista Network Attack Surface Analysis: A Broad Overview.

Although these problems have subsequently been fixed in the more recent build 5384, the fact that Vista exhibited a new class of security and stability issues was probably indicative of what lay ahead for the months after it first ships. The current developer build of Vista is 5472.

"Vista is one of the most important technologies that will be released over the next year, and people should understand the ramifications of a virgin network stack," Oliver Friedrichs of Symantec said.

But Microsoft had a robust response: "Given that Windows Vista is still in the beta stage of the development and not yet final, the claims made in this report are, at best, premature."

Symantec’s story will look to some like a competitive swipe, now that the two are direct competitors in the market for add-on security software. As valid as the criticisms might be, the fact that a brand new operating system exhibits a previously unknown set of security issue, is hardly surprising.

More important will be the number of security updates Microsoft finds itself having to issue in the first months of its existence, and the ability of business users to adapt to some of its new - and potentially problematic - features such as IPv6 support.