Malicious Software Encyclopedia: TrojanDownloader:Win32/Clagger.C
Published:
January 25, 2007
TrojanDownloader:Win32/Clagger.C is a trojan downloader that downloads a particular file from a specific URL and runs that file. The trojan registers itself as an authorized application with the Windows firewall in order to access the Internet without interference from the firewall.
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Threat Overview
| Class/type | Trojan - Downloader
|
| Discovered | October 7, 2008 |
| Circulating | Yes |
| Affected operating systems | Windows NT 4.0
Windows 95
Windows 2000
Windows XP
Windows Server 2003
Windows ME
Windows 98
|
| Affected software |
Not specified
|
| Infection rating | Low |
| Recovery difficulty | Easy |
| Damage rating | Low |
| Transmission rating | Low |
Aliases (Also Known As)
Different antivirus vendors may be using different names to refer to this malicious software. Here are some of the names currently in use by antivirus software vendors participating in the Microsoft Virus Information Alliance (VIA):
CA:
Win32/Clagger.5944!TrojanKaspersky:
Trojan-Downloader.Win32.Agent.aduMcAfee:
Downloader-ATM!CME-934Sophos:
Troj/Clagger-K
Learn more about the
Microsoft Virus Information Alliance.
Technical Analysis
TrojanDownloader:Win32/Clagger.C is a trojan downloader.
In order to access the Internet without interference from the Windows firewall, the trojan registers itself as an authorized application with the firewall by modifying the registry as follows:
Adds value: <trojan file name>
with data: <path to trojan>:*:enabled:earthwormjimm
under registry key:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\firewallpolicy\standardprofile\authorizedapplications\list
TrojanDownloader:Win32/Clagger.C then downloads a particular file from a specific URL to the host computer. The trojan saves the downloaded file to %windir%\ndppbzn.exe and runs the file. The trojan also drops a batch file to C:\1.bat and runs that file. The batch file attempts to delete the original trojan downloader file, and then deletes itself.
How to Prevent Infection
Take the following steps to help prevent infection on your system:
Enable a firewall on your computer.
Get the latest computer updates.
Use up-to-date antivirus software.
Use caution with attachments and file transfers.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows XP Internet Connection Firewall.
To turn on the Internet Connection Firewall in Windows XP
Click Start, and click Control Panel.
Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
Click Change Windows Firewall Settings.
Select On.
Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. You can use the Automatic Updates feature in Windows XP to download future Microsoft security updates automatically while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows XP
Click Start, and click Control Panel.
Click System.
Click Automatic Updates.
Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
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 that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/athome/security/downloads/default.mspx
Use caution with attachments and 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.
How to Tell If Your Computer Is Infected
Symptoms of an infection by TrojanDownloader:Win32/Clagger.C may include the following:
- Presence of a file named ndppbzn.exe in %windir%, the Windows folder. (By default, the Windows folder is C:\Windows on Windows 95/98/ME/XP/Server 2003, or C:\WINNT on Windows NT/2000.)
- Presence of data containing the string: earthwormjimm
in registry key:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\firewallpolicy\standardprofile\authorizedapplications\list
How to Recover from Infection
Automatic Recovery
To attempt to automatically remove this threat, run one of the following removal tools:
Manual RecoveryTrojanDownloader:Win32/Clagger.C downloads and installs additional malicious software, thus manual removal is not recommended. To detect and remove this trojan and other software that it may have installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft online scanner (http://safety.live.com). For more information, visit http://www.microsoft.com/athome/security/downloads/default.mspx
Payload Information
| Payload type | Trigger | Description |
|---|
| Compromises Security | Execution | - Registers itself with the Windows firewall
- Downloads a file from a URL and runs the file
|
Modified Registry Entries
| Changed registry entries |
|---|
| Key | HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\firewallpolicy\standardprofile\authorizedapplications\list |
| Value name | <trojan file name> [String] |
| Old value | |
| New value | <path to trojan>:*:enabled:earthwormjimm [String] |
Dropped Files
