Adware, a malware-serving Trojan, and a fake security program are at the top of May's e-threats list, issued by security vendor BitDefender earlier today.

The top menace of the month is Trojan.Clicker.CM, a popup-ad-serving trojan distributed via infected Websites. In order to successfully display the popups containing advertisements, the trojan has the ability to bypass the Norton Internet Security Popup Blocker, BitDefender says.

In second place is Trojan.Downloader.WMA.Wimad.N. Despite the complicated-sounding name, this trojan serves a very simple function: to load another piece of malware. It does so by pretending to be a helper application that downloads a "codec" playing a "special type" of WMA file, according to BitDefender.

Once the user is tricked, it downloads and runs Adware.PlayMp3z.A, an application meant to take personal information from the computer and use it for marketing or suspicious practices. When executed, the adware displays a popup with an end user licensing agreement in an attempt to convince users of its legitimacy.

In third place -- proving once again that security is big business -- is a fake (or rogue) antivirus installer, which purports to install "XP antivirus." Once installed, XP antivirus claims to have found viruses on the victim's computer and requests money "for activation" to remove them, Bitdefender says.

"Adware is the word of the month and that is because it makes money without posing so much legal risk," said Sorin Dudea, head of BitDefender AV Research. "We may see more of these and similar threats in the months to come."

— Tim Wilson, Site Editor, Dark Reading