First it was viruses, then it was Trojans, next came worms, and of course then came spam. Now rootkit infections are on the rise, according to Prevx, makers spyware and malware detection and remediation technologies.

The company tracks statistics from users of its free Computer Security Investigator (CSI) tool. In October about 290,600 users installed CSI. Of those users 42,250 had spyware or other malware on their systems.

In December Prevx added rootkit detection to CSI and another 420,000 users installed the software. Approximately 115,000 ran CSI with rootkit detection enabled and nearly 1700 systems had some type of rootkit. Prevx's data indicates that 1 in 70 computers has a rootkit, which the company said is much higher than previously expected.

The picture isn't any better for businesses. A spokesperson for Prevx said that in the firsts 9 days of December, 93 companies took advantage of Prevx's scanning service and 13 found that at least one of their systems had become infected with a rootkit.

Another interesting finding is that of the 420,000 user's computers scanned in December, 77 percent had anti-virus and anti-malware software install. Even so, nearly 19 percent of those computer still had viruses and malware on their systems, which can be interpreted to mean that existing anti-virus and anti-malware defense software is inadequate and that users of those solutions aren't using them as effectively as they could.