Win32/Taterf is a family of worms that spread via mapped drives in order to steal login and account details for popular online games.

What to do now

Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as Microsoft Security Essentials, or the Microsoft Safety Scanner. For more information about using antivirus software, see

Threat behavior

Win32/Taterf is a family of worms that spread via mapped drives in order to steal login and account details for popular online games.
When executed, Taterf copies itself to the system directory as a hidden file using one of the following  file names:
  • amvo<number>.exe
  • kavo<number>.exe
  • awda<number>.exe
  • avpo<number>.exe
  • cyban.exe
The registry is modified to run the copy at each Windows start (for example):
Adds value: "amva"
With data: "<system folder>\amvo<number>.exe"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Run
Adds value: "avpa"
With data: "<system folder>\avpo<number>.exe"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Run
Note: Filenames and registry modifications differ according to variant.
The functionality to perform Taterf's password-stealing payload is contained in a dll component which is also dropped to the system directory using one of the following file names:
  • amvo<number>.dll
  • avpo<number>.dll
  • kavo<number>.dll
  • cyban<number>.dll
  • <random 7 or 8 letter name>.dll
Where <number> may be omitted entirely, or be a numeral from 0-9.
Once dropped, the dll is injected into explorer.exe or iexplore.exe. These dlls may be detected as Worm:Win32/Taterf.<variant letter>.dll, according to variant.
It should be noted, that in order to evade detection, the authors of this family may pack the worm's executable. In cases such as these, the worm may be detected with the following names:
  • VirTool:Win32/Vanti.A
  • VirTool:Win32/Vanti.B
  • VirTool:Win32/Obfuscator.T
A driver with a randomly generated file name may also be dropped in the %temp% directory depending on 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 removable and network drives
The worm continually enumerates drives from C- Z, copying itself to the root of the drive, and creating an 'autorun.inf' file, which points to one of the copies that it creates. When the removable or networked drive is accessed from another computer supporting the Autorun feature, the malware is launched automatically. This 'autorun.inf' file is detected as Worm:Win32/Taterf!inf.
The name that the worm uses to copy itself to in the root of the drive differs across variants, however, it usually consists of random letters and numbers with a '.com', 'cmd' or an '.exe' extension.
For example:
Steals online game data
Once injected, the DLL is used to 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
Legend of Mir
World Of Warcraft 
As part of this process, Worm:Win32/Taterf may monitor the following processes related to online games:
The captured details are sent to a remote server.
Modifies system settings
Win32/Taterf modifies the following registry modifications, which specify how hidden folders and files are displayed using Windows Explorer:
Downloads arbitrary files
The worm contacts the a specific domain in order to download files and update itself. In the wild, we have observed the malware contacting the following Web sites to download arbitrary files:
Modifies system security settings 
The worm 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.
Analysis by Matt McCormack


System Changes
The following system changes may indicate the presence of Worm:Win32/Taterf.gen:
  • Presence of any of the following files:
    <random 7 or 8 letter name>.dll
  • Where <number> may be omitted entirely, or be a numeral from 0-9


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 Web pages.
  • 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 Web sites.
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
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 e-mail 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 Web pages
Exercise caution with links to Web pages that you receive from unknown sources, especially if the links are to a Web page 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 Web page 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 8 characters, and combines letters, numbers, and symbols. For more information, see

Alert level: High
This entry was first published on: Jun 03, 2008
This entry was updated on: Apr 17, 2011

This threat is also detected as:
No known aliases