Ranking second with 8.54 percent of the worldwide infections, Trojan.AutorunInf.Gen is a generic mechanism used to spread malware via removable devices such as flash drives, memory cards or external hard-disk drives. Win32.Worm.Downadup si Win32.TDSS are two of the most famous families of malware to use this approach to trigger newer infections.
Win32.Worm.Downadup takes third position with 5.29 percent of the total amount of infected machines. Also known as Conficker or Kido, the worm restricts access to the websites associated with IT security vendors. More than that, the latest variant of the worm installs rogue security software on the compromised machines.
Trojan.Wimad comes in fourth place with 4.90 percent of the global infections. It takes advantage of a less-known feature implemented by Microsoft in order to store coordinated digital media data. The Trojan affects ASF files, an extensible file format that supports data delivery over a wide variety of networks and is extremely easy to play back locally. A specially crafted ASF file abuses the feature which allows it to download the appropriate codec in order to install Trojans instead.
Win32.Sality.OG takes the sixth position with 2.31 percent of the infections triggered globally. It is a polymorphic file infector that appends its encrypted code to executable files (.exe and .scr binaries). In order to hide its presence on the infected machine, it deploys a rootkit and attempts to kill antivirus applications installed locally.
The seventh place goes to Trojan.Autorun.AET at 2.20 percent of global infections, a malicious code spreading via the Windows shared folders, as well as through removable storage devices. The Trojan exploits the Autorun feature implemented in Windows for automatically launching applications when an infected storage device is plugged in.
Worm.Autorun.VHG is an Internet /network worm that exploits the Windows MS08-067 vulnerability in order to execute itself remotely using a specially crafted RPC (remote procedure call) package (an approach also used by Win32.Worm.Downadup). The worm ranks eight with 1.49 percent of the global infections.
Trojan.Swizzor.6 is yet another variant of the Swizzor family, "obfuscated" downloaders that would try to save and execute new threats on infected machines. The Trojan adds its key to the Windows Registry in order to execute a copy of itself each time Windows is started. This specific variant of Swizzor accounts for 1.22 percent of the global infections.
Ranking last in this month's Top Ten E-threats, Gen:[email protected] scores 1.21 percent of the global infections. This generic routine detects a wide range of adware applications, especially the NaviPromo family.
BitDefender's October 2009 Top 10 E-Threat list includes: