According to Symantec, this Trojan can deny you control of the PC. Blocking websites may be one of these denials.
http://securityresponse.symantec.com/avcenter/venc/data/backdoor.dvldr.html
This is what Symantec report for Win2000....
1. Update the virus definitions.
2. Windows NT/2000/XP: End the Trojan process.
3. Run a full system scan and delete all the files detected as Backdoor.Dvldr.
4. Reverse the changes that the Trojan made to the registry.
Windows NT/2000/XP
To end the Trojan process:
a. Press Ctrl+Alt+Delete once.
b. Click Task Manager.
c. Click the Processes tab.
d. Double-click the Image Name column header to alphabetically sort the processes.
e. Scroll through the list and look for the following:
explorer.exe
NOTE: If the Trojan is running, you will see two explorer.exe entries in the list. To find which is the AT&T VNC server for each explorer.exe entry, look at the values for PID and Mem Usage. The AT&T VNC server disguised as explorer.exe will have a higher PID number and lower Mem Usage than the legitimate explorer.exe.
rundll32.exe
f. For each one that you find, click it, and then click End Process.
g. Exit the Task Manager.
4. Reversing the changes made to the registry
CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.
a. Click Start, and then click Run. (The Run dialog box appears.)
b. Type regedit
Then click OK. (The Registry Editor opens.)
c. Navigate to the key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
d. In the right pane, delete these values:
Explorer %windows%\Fonts\explorer.exe
TaskMan %windows%\Fonts\rundll32.exe
e. Exit the Registry Editor.
