disabling 'connect as'

[Blair, Jason]

Our network was hit with the Nimba virus. All of the computers in our
control are protected. Rouge computers, however, can map to our drives
using the 'connect as', 'connect using different user name', or
passthrough authentication. These rouge computers keep writing the virus
back up to our shares. 
 
Is there any way to prevent this?
 
-Jason Blair
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