Troj/Spy-BL is a backdoor Trojan that allows a remote intruder to gain access and control over the computer.

When Troj/Spy-BL is installed the following files are created:

System\netwp.sys
System\netwrp.dll

The file netwrp.dll is detected as Mal/Emogen-U.

More information can be found at this Sophos page.