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Autorun-based malware tops BitDefender’s November Top Ten Threat Report

Trojan.AutorunInf.Gen moves out of second place to take the lead.

BitDefender’s Top Ten Threat Report for November is topped by Trojan.AutorunInf.Gen. Trojan.AutorunInf.Gen, which came in second place on October’s list, is a generic family of malware abusing the Autorun feature in Microsoft Windows operating systems. By default, every removable storage device features an autorun.ini script that instructs the computer which file to execute when the medium is plugged in. Malware authors frequently tamper with the file to make it launch miscellaneous malicious applications.

Trojan.Clicker.CM moves down a spot, ranking second with nearly 8% of total infections. Trojan.Clicker.CM is found on websites hosting illegal applications such as cracks, keygens and serial numbers for popular commercial software applications. Clicker.CM is used to force advertisements inside a user’s browser in order to boost advertisement revenue.

Coming in third on this month’s threat report is Win32.Worm.Downadup.Gen.  Responsible for almost 6% of global infections, Win32.Worm.Downadup.Gen relies on the Microsoft Windows Server Service RPC Handling Remote Code Execution Vulnerability (MS08-67) in order to spread onto other computers in the local network. It also restricts users’ access to Windows Update and security vendor websites. Newer variants of the Downadup worm install rogue antivirus applications, among others.

Trojan.Wimad takes fourth place with over 5% of global infections. Trojan.Wimad exploits the capability of ASF files to automatically download the appropriate codec from a remote location in order to deploy infected binary files on the host system.

Exploit.PDF-JS.Gen is a generic detection for specially crafted PDF files which exploit different vulnerabilities found in Adobe PDF Reader's Javascript engine in order to execute malicious code on a user's computer. Upon opening an infected PDF file, a specially crafted Javascript code triggers the download of malicious binaries from remote locations. Exploit.PDF-JS.Gen comes in fifth with 3,23% of the global infections.

Win32.Sality.OG ranks sixth with 2,57% of the infections triggered globally. Win32.Sality.OG 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 spot BitDefender’s November Top Ten Threat Report goes to Trojan.Autorun.AET, a malicious code spreading via the Windows shared folders, as well as through removable storage devices. Trojan.Autorun.AET 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. This approach is also used by Win32.Worm.Downadup. Worm.Autorun.VHG ranks eight with 1,59% of global infections.

Trojan.Inject.RA is a password-stealing Trojan that mostly targets Lineage II computer players. This specific variant has a keylogging component that intercepts users’ keystrokes and sends them to a remote attacker via HTTP or SMTP protocols.

Trojan.Downloader.Bredolab.AZ rounds out the list in tenth place with 1,20% of globally infected systems. Disguised as a Microsoft Word document, the Trojan drops a DLL file and registers it as a Browser Helper Object. Trojan.Downloader.Bredolab.AZ monitors users’ keyboard input via a keylogging component and sends the data to a website located in Russia.

BitDefender’s November 2009 Top 10 E-Threat list includes:

1 Trojan.AutorunINF.Gen 8,45

2 Trojan.Clicker.CM 7,87

3 Win32.Worm.Downadup.Gen 5,62

4 Trojan.Wimad.Gen.1 5,00

5 Exploit.PDF-JS.Gen 3,23

6 Win32.Sality.OG 2,57

7 Trojan.Autorun.AET 2,05

8 Worm.Autorun.VHG 1,59

9 Trojan.Inject.RA 1,45

10 Trojan.Downloader.Bredolab.AZ 1,20

Others 60,97

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