W32/Dasher-B is a worm for the Windows platform.
W32/Dasher-B spreads by exploiting the MSDTC (MS05-051) vulnerability.
When run the worm creates the following files :
<Windows system folder>\wins\sqlexp.exe
<Windows system folder>\wins\sqlscan.exe
<Windows system folder>\wins\svchost.exe
Sqlscan.exe is a port scanner, used to search networks for open ports.

Sqlexp.exe and svchost.exe are detected as W32/Dasher-B.
W32/Dasher-B searches a set of pre-defined networks for open ports and attempts to exploit and vulnerable computers it finds. The exploit opens a backdoor on the vulnerable computer and causes it to connect to a remote server for further instructions.

At the time of writing the instructions supplied by the remote server cause the exploited computer to download and execute two further programs.