. . .to insert a dialogue box asking for passwords involves a deliberate penetration of the machine. This may have been a passive intrusion through a spiked download or, more seriously, it could have been a backdoor entry. If the former, this may be a simple fishing expedition and, by not responding, you preserve your system's integrity (assuming there is no automatic notification script built into the Trojan). If the latter, the intruder already has the target computer's address and "blocking" the IP will be ineffective. Hence, the question is how seriously we should treat the matter. If Michaellloyd runs a small system out of his home with nothing incriminating or sensitive on his machine (like his credit card details and handshaking routines for different on-line shopping sites), we could advise him to ignore the problem. Had the intruder intended anything malicious, it would more than likely already have shown up. But this could have been a crawler survey preparing to highjack his e-mail server for distributing spam, or he may have employment requiring him to process commercially sensitive information on his machine which should be protected. Hence, the point of my question.