Adware has been the most damaging type of spyware in March. Sixty-eight percent of all spyware detected by the online antivirus company Panda was adware. This type of malware is designed to show unwanted pop-up ads.

The second most active type of spyware in March were PUPs (Potentially Unwanted Programs), which accounted for 24 percent of spyware infections detected.

Finally, spyware aimed at collecting data about users' Internet habits, represented eight percent of the total.

"Adware is a type of spyware that generates substantial economic benefits for its creators. They get money from companies paying for having their ads shown, but there are also dubious marketing companies that create adware and pay third parties for installing it on computers," says Luis Corrons, technical director of PandaLabs.

No major changes occurred in the March ranking of the most active spyware, which is once again headed by Lop. This is an adware that displays ads and installs a search bar on the Internet Explorer browser. The old-timer Gator, another adware, is second on the list. Third place is taken by the MyWebSearch PUP, which installs a search bar on the browser.

SaveNow, an adware that offers information about the weather in exchange for the user viewing certain ads, is in fourth place. Fifth and sixth were the nCase adware and the WinAntivirus2006 PUP respectively.

It's in the seventh position where the changes begin compared to last month's ranking. The VideoActiveXObject adware moves up one spot and relegates wupd to eighth place.

Ninth place is occupied by the only new addition to the list: Virtumonde, a key-logging spyware that also shows ads.

The CWS adware is last on the list, moving down one place compared to last month.

Name Previous position
Adware/Lop1 =
Adware/Gator2 =
Application/MyWebSearch3 =
Adware/SaveNow4 =
Adware/nCase5 =
Application/Winantivirus20066 =
Adware/VideoActiveXObject8 +
Adware/WUpd7 -
Spyware/Virtumonde New
Adware/CWS9 -