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Backdoor:Win32/Xtrat.A


Backdoor:Win32/Xtrat.A is a trojan that allows unauthorized access and control of an affected computer.


What to do now

To detect and remove this threat and other malicious software that may have been installed in your computer, run a full-system scan with an up-to-date antivirus product such as the following: For more information about using antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Threat behavior

Backdoor:Win32/Xtrat.A is a trojan that allows unauthorized access and control of an affected computer.
Installation
When executed, Backdoor:Win32/Xtrat.A copies itself to c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe.

The malware modifies the following registry entries to ensure that its copy executes at each Windows start:

Adds value: "HKLM"
With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

Adds value: "HKCU"
With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
To subkey: HKCU\Software\Microsoft\windows\currentversion\run

Adds value: StubPath
With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
To subkey: hklm\software\microsoft\active setup\installed components\{4c545v67-vdf7-r23m-6j1p-131bxv0a7x27}

The malware creates the following files on an affected computer:

  • c:\documents and settings\administrator\application data\microsoft\windows\--((mutex))--.xtr

The malware utilizes code injection in order to hinder detection and removal. When Backdoor:Win32/Xtrat.A executes, it may inject code into running processes, including the following, for example:

  • IEXPLORE.EXE
  • svchost.exe

Payload
Modifies browser settings
Backdoor:Win32/Xtrat.A locks the Internet Explorer toolbar by making the following registry modification:

Adds value: "Locked"
With data: "1"
To subkey: HKCU\Software\Microsoft\Internet Explorer\Toolbar

Allows backdoor access and control
The malware allows unauthorized access and control of an affected computer. An attacker can perform any number of different actions on an affected computer using Backdoor:Win32/Xtrat.A. This could include, but is not limited to, the following actions:

  • Download and execute arbitrary files
  • Upload files
  • Spread to other computers using various methods of propagation
  • Log keystrokes or steal sensitive data
  • Modify system settings
  • Run or terminate applications
  • Delete files

This malware description was produced and published using our automated analysis system's examination of file SHA1 3dee531e2ee60eee11024d08a9a00afd24283647.

Symptoms

System changes
The following system changes may indicate the presence of this malware:

  • The presence of the following files:
  • c:\documents and settings\administrator\application data\microsoft\windows\--((mutex))--.xtr
    c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe

  • The presence of the following registry modifications:
  • Adds value: "HKLM"
    With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
    To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    Adds value: "HKCU"
    With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
    To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Run

    Adds value: StubPath
    With data: "c:\documents and settings\administrator\local settings\temp\xtreme\xtremeserver.exe"
    To subkey: hklm\software\microsoft\active setup\installed components\{4c545v67-vdf7-r23m-6j1p-131bxv0a7x27}

    Adds value: "Locked"
    With data: "1"
    To subkey: HKCU\Software\Microsoft\Internet Explorer\Toolbar


Prevention


Alert level: Severe
First detected by definition: 1.103.1798.0
Latest detected by definition: 1.189.471.0 and higher
First detected on: May 16, 2011
This entry was first published on: May 23, 2011
This entry was updated on: May 23, 2011

This threat is also detected as:
No known aliases