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Win32/Frethog


Win32/Frethog is a large family of password-stealing trojans that target confidential data, such as account information, from Massive Multiplayer Online Games (such as World of Warcraft, for example).


What to do now

To detect and remove this threat and other malicious software that may be installed on your computer, run a full-system scan with an appropriate, up-to-date, security solution. The following Microsoft products detect and remove this threat:
 
 
For more information on antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Threat behavior

Win32/Frethog is a large family of password-stealing trojans that target confidential data, such as account information, from Massive Multiplayer Online Games (such as World of Warcraft, for example). Some variants of Win32/Frethog are also able to spread via mapped drives by utilizing an autorun file.
Installation
Win32/Frethog is a large family and variants may install themselves using different file paths and file names.

When executed, Win32/Frethog drops a dll with a randomly generated file name and injects it into explorer.exe.
 
The dropper may then modify the following registry entries in order to execute itself at each Windows start:
HKEY_CURRENT_USER\SoftWare\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\SoftWare\Microsoft\Windows\CurrentVersion\Run
which packer is used. This driver is detected as either VirTool:WinNT/Vanti.A or VirTool:WinNT/Vanti.B. The above mentioned dlls may also be written to the %temp% directory when these packers are used.
Spreads Via...
Mapped Drives
Some variants of Win32/Frethog are also able to spread via mapped drives by utilizing an autorun file. TWin32/Frethog may enumerate drives from C- Z, copying itself to the root of the drive, and creating an 'autorun.inf' file. The autorun.inf is used to execute the worm whenever the drive is viewed with Windows Explorer.
Payload
Modifies System Security Settings 
The dropper attempts to circumvent security products by:
  • Attempting to prevent AVP Antivirus from displaying notifications regarding system changes by closing windows used by this product.
  • Attempting to terminate Ravmon.exe if it is found to be running on the affected system.
 
Steals Online Game Data
The dll, once injected, can obtain account information for one or more of the following Massively Multiplayer Online Games and affiliated products:
Rainbow Island
Cabal Online
A Chinese Odyssey
Hao Fang Battle Net
Lineage
Gamania
MapleStory
qqgame
Legend of Mir
World Of Warcraft 
 
The captured details are sent to a remote server.
 
Analysis by Matt McCormack

Symptoms

There are no obvious symptoms that indicate the presence of this trojan on an affected system.

Prevention

Take the following steps to help prevent infection on your computer:
  • Enable a firewall on your computer.
  • Get the latest computer updates for all your installed software.
  • Use up-to-date antivirus software.
  • Limit user privileges on the computer.
  • Use caution when opening attachments and accepting file transfers.
  • Use caution when clicking on links to webpages.
  • Avoid downloading pirated software.
  • Protect yourself against social engineering attacks.
  • Use strong passwords.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites.
 
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software, such as Microsoft Security Essentials, that is updated with the latest signature files. For more information, see http://www.microsoft.com/windows/antivirus-partners/.
Limit user privileges on the computer
Starting with Windows Vista and Windows 7, Microsoft introduced User Account Control (UAC), which, when enabled, allowed users to run with least user privileges. This scenario limits the possibility of attacks by malware and other threats that require administrative privileges to run.
 
You can configure UAC in your computer to meet your preferences:
Use caution when opening attachments and accepting file transfers
Exercise caution with email and attachments received from unknown sources, or received unexpectedly from known sources. Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to webpages
Exercise caution with links to webpages that you receive from unknown sources, especially if the links are to a webpage that you are not familiar with, unsure of the destination of, or suspicious of. Malicious software may be installed in your computer simply by visiting a webpage with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information, see 'The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software to compromise a computer, they also attempt to exploit vulnerabilities in human behavior to do the same. When an attacker attempts to take advantage of human behavior to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted computer. For more information, see 'What is social engineering?'.
Use strong passwords
Attackers may try to gain access to your Windows account by guessing your password. It is therefore important that you use a strong password – one that cannot be easily guessed by an attacker. A strong password is one that has at least eight characters, and combines letters, numbers, and symbols. For more information, see http://www.microsoft.com/protect/yourself/password/create.mspx.

Alert level: Severe
This entry was first published on: May 26, 2008
This entry was updated on: Apr 17, 2011

This threat is also detected as:
No known aliases