As many as one in six PCs may have active spyware or malware infections.

A recent study performed by U.K. security vendor Prevx of 300,000 PCs showed that 15.6 percent of those machines had at least one active spyware or malware program installed. These programs, which include keyboard loggers that record keystrokes, information stealers and fake antispyware, are emerging at rates of 5,000 to 10,000 per day, company officials say.

Of these 300,000 PCs, the ones with no security software installed at all had infections rate 60 percent higher than those running some sort of antivirus, antimalware, or other security program.

Prevx makes software that scans PCs for malware and spyware and is available as a free download. The company says users benefit from running the scan because not only will it reveal the hidden programs on a computer, but will also force users to think twice about their surfing habits. Malware and spyware is often downloaded in the background from Web sites, many of which are known to spread unwanted or malicious code.

Prevx also says that of the business customers that run the free scan today, on average 59.5 percent find at least one infected PC in their organization.

The company claims that major security vendors aren't keeping up with malware writers. Over the past three months, the ability of security software from Microsoft, Symantec, and Trend Micro to detect newly released spyware and malware hovered between 10 and 50 percent, they say.