Win32/Taterf threat description - Microsoft Security Intelligence

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.

Installation

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:

q.com

d.com
d6fagcs8.cmd
gjn2pjlw.exe
h1dwg20.exe
h6o0re.cmd

Payload

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
Lineage
Gamania
MapleStory
qqgame
Legend of Mir
World Of Warcraft

As part of this process, Worm:Win32/Taterf may monitor the following processes related to online games:

amo.exe

cabalmain.exe

cc.exe

client.exe

dakerden.exe

dakeron.exe

dnf.exe

ffclient.exe

ge.exe

gersang.exe

goonzu.exe

hevaonline.exe

inphasenxd.exe

knightonline.exe

main.exe

maplestory.exe

mir3game.exe

mixer.exe

nida.exe

so3d.exe

winbaram.exe

wow.exe

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:

HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\NoDriveTypeAutoRun

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\ShowSuperHidden

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Hidden
HKLM\Software\Microsoft\Windows\CurrentVersion\explorer\Advanced\Folder\Hidden\SHOWALL\CheckedValue

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:

om7890.com
googlew65.com
yahooui0.com

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

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 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 http://www.microsoft.com/security/antivirus/av.aspx.

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 http://www.microsoft.com/protect/yourself/password/create.mspx.

Win32/Taterf

Summary

What to do now

Technical information