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F-Secure Malware Information Pages: Trojan-Downloader:W32/Exchanger
[Summary] | [Disinfection] | [Details] | [Additional Details]

Name : Trojan-Downloader:W32/Exchanger
Detection Names : Trojan-Downloader:W32/Exchanger
Trojan-Downloader.Win32.Exchanger
Type:Trojan-Downloader
Category:Malware
Platform:W32
Radar

Summary
Trojan-Downloader:W32/Exchanger variants download additional malicious software onto the infected system.
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Disinfection

To manually remove a Trojan-Downloader:W32/Exchanger infection, perform the following steps:

  1. Open the Windows Task Manager by pressing the Ctrl + Alt + Delete keys and click the Task Manager button.
  2. From the list of running processes, find CbEvtSvc.exe and then click the End Process button.
  3. You may close the Task Manager once the malicious process is terminated.
  4. From the Windows Start Menu, select Run, type regedit into the "Open:" field and then click OK.



  5. From the Registry Editor, locate and delete the following keys if present:
    • HKLM\SYSTEM\CurrentControlSet\Services\CbEvtSvc
    • HKLM\SYSTEM\ControlSet001\Services\CbEvtSvc
    • HKLM\SYSTEM\ControlSet002\Services\CbEvtSvc
    Note: HKLM equals HKEY_LOCAL_MACHINE
  6. Delete the file called CbEvtSvc.exe located in the C:\WINDOWS\system32\ folder.
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Details


File System Changes
Creates these files:

  • %windir%\system32\CbEvtSvc.exe



Process Changes
Creates these processes:

  • %windir%\system32\CbEvtSvc.exe



Registry Modifications
Sets these values:

  • HKLM\System\CurrentControlSet\Services\CbEvtSvc
    Type = 00000010
    Start = 00000002
    ErrorControl = 00000001
    ImagePath = %SystemRoot%\System32\CbEvtSvc.exe -k netsvcs
    DisplayName = CbEvtSvc
    ObjectName = LocalSystem
    Opt =
  • HKLM\System\CurrentControlSet\Services\CbEvtSvc\Security
    Security = \x01\x00\x14\x80\x90\[...]


Creates these keys:

  • HKLM\System\CurrentControlSet\Services\CbEvtSvc
  • HKLM\System\CurrentControlSet\Services\CbEvtSvc\Security
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Additional Details
Once the trojan is executed it copies itself into the "system32" folder and starts itself from there as a service.

The trojan also creates Windows registry entries to ensure that it is started every time the computer is started.

Once running, Exchanger variants will attempt to contact a remote server in order to relay information about the infected machine. The server will reply with a list of URLs that point to malicious files to be downloaded.
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F-Secure Corporation

Last Modified: August 29, 2008