Microsoft insists that Windows Vista is its most secure desktop operating system ever, claiming it recorded about half as many vulnerabilities in its first full year of availability as Windows XP did in its opening 12 months.

In an update to earlier 90-day and six-month reports, Jeff Jones, a security strategy director in the company's Trustworthy Computing group, cited vulnerability and patch statistics to show that Vista logged 66 total bugs between November 2006 and November 2007, 30 of which had not yet been patched. In the first 52 weeks Windows XP was in use, on the other hand, it was pegged with 129 vulnerabilities, 54 of which were not fixed by the end of that 12-month period.

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Others at Microsoft used Jones' statistics to claim that Vista is more a more secure OS than XP. "I think that it's fair to say that Windows Vista is proving to be the most secure version of Windows to date," said Austin Wilson, a director in Microsoft's Windows client group, in a post to the Vista Security blog. "Our investments in SDL [Security Development Lifecycle] and our defence-in-depth approach to building Windows Vista seem to be paying off."

Wilson touted Internet Explorer 7.0's 'Protected Mode' - a sandbox-style security provision available only in the Vista edition of the browser - and Vista's own User Account Control (UAC) as reasons why the OS is more secure. "Of the 23 security bulletins that have been released for Windows Vista through January 2008, 12 specifically call out a lower impact for those running without administrative privileges," noted Wilson. "This is a great illustration of the importance of User Account Control and why we included it in the product."

But numbers don't tell the whole story, countered a pair of security professionals.

"As a lot of people have said, Gartner included, [corporate] switching to Vista has been a slow process," said John Pescatore, the research firm's security guru. "Microsoft has said all along that Vista would be a big leap in security, and it's been on that drum beat. Everybody does that. Oracle, Sun, Red Hat, they all say that they have fewer patches than the other.

"But Vista is definitely a major [security] improvement over XP."

Andrew Storms, research director at security vendor nCircle, agreed. "The year-one for Vista and year-one for XP clearly show that Vista has had fewer vulnerabilities than XP. That's a good sign for Microsoft and the enterprise - and consumers."

Even so, both Pescatore and Storms question the worth of bug counts, as well as some of Microsoft's measurements. "More important than the number of vulnerabilities is what attacks are targeting and how much pain there is in entering patches," said Pescatore. "That should be the real measurement."

In other words, a vulnerability in Vista or XP should not be treated as the equal of one in say, a Linux distribution. The former, because of the widespread use of Windows and much greater interest on the part of attackers to exploit the OS's weaknesses, must be patched without delay. The latter? "For most companies that use Linux on the desktop, they can patch in a much more leisurely fashion," said Pescatore. That's because they know the likelihood of an attack is slim.

Storms came to a similar conclusion, but for a different reason. "Outside of the Vista-to-XP, comparisons are a moot point," added Storms, referring to the section of Jones' report where Vista's vulnerability count was compared against Mac OS X, Red Hat Enterprise Linux and Ubuntu Linux. "You just can't compare Vista to Linux," said Storms. "There are simply too many variables. I'd argue the same for Mac OS."

Nor, said Pescatore, should all of Microsoft's conclusions be taken as gospel. "Patch events," which both Jones and Wilson cited, is a good example.

According to Microsoft, patch events is the number of times a company has to activate its patch management process because a vendor has issued a security update. Jones, for example, contrasted Vista's nine patch events in its first 12 months with XP's 26 although, as he acknowledged, XP's events were spread across more days because Microsoft had not yet moved to a monthly patch schedule.

"Patch events don't take into account the days spent making sure an enterprise's applications will work once a patch is deployed," countered Pescatore.

And just as a vulnerability on one OS shouldn't be equated with one on a different OS, patch events aren't comparable, either. "It's a fact that when 'Patch Tuesday' comes around and there are critical Windows patches, you have to start calling overtime. With other products, [those patches] can wait until the end of the month," Pescatore said.

But while he questioned some aspects of Jones' report too, nCircle's Storms gave Microsoft an 'A' for effort. "It's worth Microsoft's time to do this, and talk about Vista like this, on a marketing level and on a public relations level. [It has] come leaps and bounds in communicating [about security] with the public.

"[It is] actually putting together numbers and releasing them," Pescatore said. "That's hard to find among OS vendors."

Jones' report can be downloaded from the Microsoft site.