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TrojanDownloader:Win32/Tracur.A


TrojanDownloader:Win32/Tracur.A is a trojan that downloads and executes arbitrary files.


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

Threat behavior

TrojanDownloader:Win32/Tracur.A is a trojan that downloads and executes arbitrary files.
Installation
When executed, TrojanDownloader:Win32/Tracur.A drops a file to <system folder>\<random>32.dll, where <random> is a randomly generated string.
 
Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.
 
The trojan also modifies the registry to make sure it is loaded into every process at each Windows restart:
 
Adds value: "DllName"
With data: "<system folder>\<dllname>",
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\<volume>
 
Modifies value: AppInit_Dlls"
With data: "<system folder>\<dllname>",
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows.

where <dllname> is the filename of the trojan's DLL, and <volume> is a string derived from the volume serial number.
Payload
Downloads and Executes Arbitrary Files
TrojanDownloader:Win32/Tracur.A listens on an undefined TCP port and waits for instructions. It may be instructed to perform the following actions:
  • Download and execute arbitrary files
  • Redirect the user's web browser to a URL of the attacker's choice, and maximize the web browser Window.
 
Analysis by Chun Feng

Symptoms

There are no obvious symptoms that indicate the presence of this malware on an affected machine.

Prevention


Alert level: Severe
This entry was first published on: Dec 16, 2008
This entry was updated on: Apr 17, 2011

This threat is also detected as:
  • Win32/Agent.OAF (ESET)
  • Win32/Vundo.BAW (CA)
  • Trojan-Downloader.Win32.Agent.afky (Kaspersky)