Skip to main content
Skip to main content
Microsoft Security Intelligence
Cart 0 items in shopping cart
Sign in
Published Jun 15, 2005 | Updated Sep 15, 2017

TrojanDownloader:Win32/Small.APT

Detected by Microsoft Defender Antivirus

Aliases: BackDoor-CST (McAfee) Backdoor.Trojan (Symantec) Win32/SillyDl.28672!Trojan (CA)

Summary

TrojanDownloader:Win32/Small.APT is a Trojan downloader that targets certain versions of Microsoft Windows. The Trojan can download and run files from an FTP server and various Web sites. It also terminates security-related processes. 
To manually recover from infection by TrojanDownloader:Win32/Small.APT, perform the following steps:
  • Disconnect from the Internet.
  • Remove the Trojan downloader service 
    or
  • Delete the Trojan downloader registry entry [Windows 9x only].
  • Restart your computer.
  • Delete the Trojan downloader folder and file from your computer.
  • Take steps to prevent re-infection.

Disconnect from the Internet

To help ensure that your computer is not actively infecting other computers, disconnect it from the Internet before proceeding. Print this Web page or save a copy on your computer; then unplug your network cable and disable your wireless connection. You can reconnect to the Internet after completing these steps.

Remove the Trojan downloader service

For computers running Windows operating systems later than Windows 9x.
To remove the Trojan downloader service
  1. On the Start menu, click Settings, then click Control Panel.
  2. Double-click Administrative Tools.
  3. Double-click Services.
  4. Right-click the service called Network Services.
  5. If the service is running, click Stop.
  6. Right-click the service again and click Properties.
  7. Under Startup Type, change the type to Disabled.

Delete the Trojan downloader registry entry

For computers running Windows 9x operating systems.
Under Windows 98, TrojanDownloader:Win32/Small.APT creates an entry in the Windows registry that causes the downloader to run every time Windows starts.
To delete the Trojan Downloader worm registry entry
  1. On the Start menu, click Run.
  2. Type regedit and click OK.
  3. In the left pane, navigate to the key:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    In the right pane, right-click the value "Network Services" if it is present. 
  4. Click Delete and click Yes to delete the value.
  5. Close the Registry Editor.

Restart your computer

To restart your computer
  1. On the Start menu, click Shut Down.
  2. Select Restart from the drop-down list and click OK.

Delete the Trojan downloader folder and file from your computer 

To delete the Trojan downloader folder and file from your computer
  1. Click Start, and click Run.
  2. In the Open field, type C:\Program Files\Internet Explorer.
  3. Click OK.
  4. Click Name to sort folders and files by name.
  5. If the folder iexplore is in the list, delete it. This will also delete the Trojan downloader file svchost.exe that the folder contains.
  6. Click Yes to confirm the deletion of the folder and file.
  7. On the Desktop, right-click the Recycle Bin and click Empty Recycle Bin.
  8. Click Yes to confirm the deletion.
If deleting the folder and file fails, follow these steps to verify that the file is not running:
  1. Press CTRL+ALT+DEL once and click Task Manager.
  2. Click Processes and click Image Name to sort the running processes by name.
  3. Confirm that svchost.exe is not in the list. 

Take steps to prevent re-infection

Do not reconnect your computer to the Internet until the computer is protected from re-infection. See the "Preventing Infection" section for more information.
Follow us