The biggest information security headache during 2009 was the Conficker.C worm, which first appeared on 31 December, 2008, and has spent the last year infecting companies and home users alike, according to PandaLabs.
The insidious and tenacious nature of the worm has earned it first place in Panda's ranking.
Another piece of malware causing severe problems during the year was the Harry Potter of viruses, Samal-A.
Although there is no reference to the world's most popular fictional wizard, the on-screen messages of the Samal.A virus are all about magic. When the virus infects a computer, users will see the message "Ah ah you didn't say the magic word" and the cursor then flickers, waiting for users to enter a word.
According to PandaLabs, it doesn't matter what is entered, because after three attempts, the phrase: "Samael has come. This the end" appears, and the PC reboots,
V for Vendetta also caused problems during 2009 and, whilst it's still unclear who exactly the real target of this worm is, DirDel.A wreaks vengeance on infected users, progressively replacing folders in different directories with copies of itself.
According to the IT security researchers, the worm is carried in a file called Vendetta.exe with a typical Windows folder icon.
The worst nuisance of the year was Sinowal.VZR, a trojan that infected thousands of computers under the guise of plane tickets supposedly purchased by the user.
The most affectionate malware of 2009 was BckPatcher.C which changes the desktop wallpaper to an image reading "virus kiss 2009" - as PandaLabs says - what a charmer!