The top of the list was dominated by e-mail threats such as the ancient Netsky.P virus and the Peed trojan. The widespread use of a Windows metafile rendering exploit surfaced at the end of 2005 and was patched against in early 2006. The only new entrant into the top ten is a recent and rather sophisticated rootkit which goes by the name of Trojan.Kobcka.A. The rootkit is probably used to hide a mass-mailer virus.”]
Source: https://www.darkreading.com/attacks-breaches/bitdefender-lists-malware-top-10