219 and router 133 relays the request as request 221 to computer 137 as is understood in the art if on the other hand signal 217 indicates that connection request 211 is to be rejected firewall 133 drops or rejects the connection request 211 as is understood in the art analogous operation can protect computers within subnet 130 from compromised devices within subnet 130 as well for example fig4 illustrates subnet 130 with computer 137 compromised under the control of a virus or worm for example computer 137 sends connection attempt 231 to router 133 in an attempt to probe or take advantage of a potential vulnerability in computer 139 on receiving connection request 231 router 133 sends relevant information about request 231 in a query 233 to security server 135 similarly to the operation discussed above in relation to fig3 security server 135 determines whether connection request 231 poses any threat and in particular any threat to software on computer 139 if so security server 135 determines whether the vulnerability has been patched and if not it determines whether computer 139 has been otherwise configured to avoid damage due to that vulnerability security server 135 replies with signal 235 to query 233 with that answer router 133 uses response 235 to determine whether to allow the connection attempt in some embodiments upon a determination by security server 135 that a connection attempt or other attack.