Trojan-Downloader:W32/Exchanger.AJ
Summary
This type of trojan secretly downloads malicious files from a remote server, then installs and executes the files.
Removal
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
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Check for the latest database updates
First check if your F-Secure security program is using the latest updates, then try scanning the file again.
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Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
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Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
Technical Details
This malware is spread via spam emails with the title "CNN Alerts". These emails are crafted to resemble a real CNN news alert email.
The spam emails contain a link or links; in this case, the links are "Usher re-hires mother as manager" and "FULL STORY". When the user clicks these links, a prompt will appear requesting the user to download and execute a file named adobe_flash.exe, which is purported to be necessary to read the full story. The downloadable file is in fact malware. Once the file is downloaded and installed, it then starts as a service and will start on every subsequent system startup as well. On execution, the malware will make a copy of itself in the Window folders with the name %windir%\system32\ as CbEvtSvc.exe. The malware will then attempt to connect to a remote server and send information about the infected system. If this connection to the remote server is established, the malware may also be instructed to download and execute additional malware onto the infected system.
Registry Modifications
Sets these values:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc Type = 00000010 HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc Start = 00000002 HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc ErrorControl = 00000001 HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc ImagePath = %SystemRoot%\System32\CbEvtSvc.exe -k netsvcs HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc DisplayName = CbEvtSvc HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc\Security Security = \x01\x00\x14\x80... HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CbEvtSvc ObjectName = LocalSystem