Win32/Conficker.B is a modified or another version of the Win32/Conficker worm which was released some time ago.
But the newly released Win32/Conficker.B is been targeted towards Microsoft Windows Server, Windows 7, Windows Vista SP1 and Windows XP SP3. The worm affects the vulnerable SVCHOST.EXE service on the Windows Server and spreads across to other computers over the network and allow remote code execution..
One of the symptoms is that users will not be able to open websites which has the following strings: microsoft, defender, virus, spyware, symantec, etc.
The following link gives more information regarding the malicious worm and the steps to prevent from it.