Microsoft's Windows Genuine Advantage has faced a whirlwind of criticism, but there should not be any complaints about the accuracy of the actual piracy check, according to Microsoft.
"The total number of what might be actual false positives found over the past year amount to only a fraction of a percent," Alex Kochis, a senior licensing manager at Microsoft, wrote on a corporate Microsoft blog this week.
About one in five of the 300 million PCs that have run WGA validations fail, according to Kochis. That is pretty much in line with industry numbers for software piracy, he wrote.
Windows Genuine Advantage is a stepped-up effort by Microsoft to boost the number of Windows users who actually pay for the operating system. The company has said that roughly a third of Windows copies worldwide have not been acquired legitimately--as a boxed product or bundled onto a machine, for example.
Microsoft has faced a lot of heat over WGA, in particular the WGA Notifications part of the antipiracy effort. It delivered a prerelease version of WGA Notifications alongside security fixes and the tool was found to ping a Microsoft server after each system restart, a behavior the company did not disclose.
Regardless, the actual check to determine whether the operating system was legitimately acquired works well, Kochis wrote. "The user might be surprised by the validation failure. Being surprised does not make the validation failure erroneous," he wrote.
When WGA validation is run, the software sends data on the system back to Microsoft. This information includes the Windows XP product key, the maker of the PC, the operating system version, PC bios information, and the user's local setting and language.
In 80 percent of the cases that systems that fail the check, a stolen license key was used, according to Kochis. "One stolen license key from a U.S. university ended up on over a million PCs in China," he wrote.
The rest of the failures are caused by a mix of other types of counterfeiting and piracy, including a variety of forms of tampering, hacking, and other forms of installing unlicensed copies, according to Microsoft.
If it turns out PC users were unknowingly victimized by a crooked software reseller, Microsoft will provide a free copy of Windows.
"So far we've provided hundreds of free copies of Windows to users who've been ripped (off by a) high-quality counterfeit, and we plan to continue this offer," Kochis wrote.