Nearly one in three computers scanned by EarthLink and Webroot in their second monthly SpyAudit were found infected with a Trojan horse or system monitor planted by spyware, the two companies said.
Internet service provider EarthLink and Webroot, a message security software maker, scanned more than 420,000 PCs during April and found nearly 134,000 Trojans or systems monitors.
So far this year, the SpyAudit has detected more than 500,000 Trojans and system monitors out of the roughly 1.5 million machines scanned. The revised numbers also showed a slight decrease in the average number of pieces of spyware per system from March to April. Scans done in April detected 26.9 spyware programs or components per machine, while March's scans found an average of 29.9. The year-to-date average is 27.5 pieces per system.
EarthLink and Webroot define spyware as any application or software that's placed on the user's machine without his or her authorization, said an EarthLink spokesman, including adware, adware cookies--typically planted to track your surfing habits for marketing and advertising purposes--Trojans, and system monitors. The best-known monitors are key loggers--software that traps every keystroke, including user names, passwords, and critical financial information like credit-card numbers, then passes them along to hackers.
"Consumers should be aware of the applications and files residing and running on their machines," Matt Cobb, EarthLink's VP of core applications, said in a statement Wednesday. "When users discover spyware, they need to take action to immediately immobilize or remove the programs."