Microsoft Windows has the lowest number of vulnerabilities and the fastest turnaround time for patches of all commercial operating systems--but it also has the most serious flaws, according to Symantec.
Despite having the fewest security holes, Windows was hit by more critical flaws than either Red Hat Linux or Mac OS X, Symantec found.
Symantec's latest "Internet Security Threat Report" (PDF) reveals 39 security holes were discovered in Windows during the second half of 2006, with an average patch development turnaround time of 21 days, up from the 22 Windows holes found in the first six months of the year.
Red Hat Linux had 208 vulnerabilities for the same period with an average patch time of 58 days, a huge increase on the 42 patched vulnerabilities for the first half of the year.
Apple's Mac OS X had 43 vulnerabilities--more than double the number for the first half of 2006--and an average patch time of 66 days.
But almost one-third of the 39 Windows holes were high severity, and 20 were medium severity. Just two of the 208 Red Hat Linux security holes discovered were high severity, with 130 medium severity and 70 low severity. Only one of the Mac OS X holes was considered high severity, with 31 classed as medium and 11 as low severity.
The report found that Windows also had the most vulnerabilities with exploit code and exploit activity, which Symantec claims may be one explanation why Microsoft has been pressured to develop and issue patches more quickly than other vendors.
Mozilla Web browsers, such as Firefox, are also more secure than Microsoft's Internet Explorer, according to the report.
It found 54 holes in IE during the second half of 2006, with one of these being of high severity, compared with 40 holes in Mozilla browsers, which had no high-severity vulnerabilities. Only four holes were found in the Safari and Opera browsers over the same period.
The latest Symantec threat report, which covers the six-month period from July 1 to December 31, 2006, also reveals the number of "zombie" PCs hijacked by hackers and used to launch denial-of-service attacks or send out spam has risen by almost 30 percent in the past year.
Arthur Wong, senior vice president for Symantec Security Response and Managed Security Services, said attack methods used by cybercriminals are becoming more complex and sophisticated to escape detection.