There are a few ways to do that.
1 would be a server logon trigger.
Another (better imho) method is to use an AD account. Then place login restrictions at the domain level for the account (http://technet.microsoft.com/en-us/library/cc781861(v=ws.10).aspx).
Another method would be via firewall rules (do you have your databases segmented from the rest of the network via firewall??).
Jason...AKA CirqueDeSQLeil
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I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
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