Corporations are under attack by the more malicious forms of spyware, a security firm said Tuesday, with the most dangerous type tripling in just two months.

The latest data from Boulder, Colo.-based Webroot's Corporate SpyAudit, a free-tool that scans enterprise desktops and networks for instances of spyware, shows that there are on average 14.5 system monitors on every 100 systems. System monitors include the most devious types of spyware, such as key loggers and screen grabbers designed to pilfer passwords and other confidential information.

Approximately 9 instances of Trojan horses were detected on every 100 desktops, Webroot added.

The last quarterly corporate spyware report from Webroot in December 2004, noted that only 5 system monitors were found on every 100 machines, and about the same number of Trojans, marking a tripling in monitors and nearly a doubling of Trojans in eight weeks.

"System monitors and Trojan horses not only present a huge risk of lost productivity, but also reveal much more devious intentions and potentially harmful economic repercussions," said Richard Stiennon, Webroot's head of threat research, in a statement.

Analysts have recently taken to pounding the pulpit about spyware, with Forrester Research's David Friedlander, for instance, predicting that a quarter of enterprise systems will be infected with spyware within the next 12 months. Webroot's figures indicate that that high infection rate is well on the way to becoming a reality.

The free Corporate SpyAudit tool can be found here.