EarthLink said that in a little over one million PC scans executed by its SpyAudit service, it found 184,559 installations of system monitor software, such as keystroke loggers, and 184,919 installations of Trojan programs.

The numbers do not necessarily indicate the same amount of unique PCs infected, but are concerning nevertheless. Trojaned machines are often used in botnets – networks of compromised zombie PCs – to carry out denial of service attacks or worse.

EarthLink actually said it found 29.5 million instances of spyware over that same one million scans, but 23.8 million of those are attributed to relatively benign cookies used by advertising networks to track user behaviour.

The firm also said it found 5.3 million instances of adware, software which ostensibly serves banner ads and sends data back to third parties without permission. EarthLink uses the free scan service to promote its Spyware Blocker software.

This article is based on material originally published by ComputerWire