A: The Delay is very important for a couple of reasons. First, each port you scan will cause over 85 bytes to be transfered over the network (the exact amount depends on the kind of network). Say that your connection can only handle 5kb per second. If you scan with a delay of 10 ms, that will generate over 8.5 kb per second, and the scan will choke. This is nothing new, the same happens with TCP port scanners. The second thing is that this UDP port scanner relies on that the scanned system sends back ICMP packets. A lot of machines limit the number of ICMP packets that may be sent in a specific time interval. The limit depends on the kind of system, sometimes a Delay of 50 ms will do, sometimes 500 ms will do, and sometimes you have to scan with a Delay of over 1000 ms. If you reach the systems limit, it will choke and you have to restart the scan. Some systems choke so bad that you can't scan them again for an hour or so. However, if you scan a Windows machine you can usually set the Delay as low as the network connection allows.

A: A packet filter that drops UDP packets from the scanner to the scanned system, and also a filter that drops ICMP packets going from the scanned system to the scanner.

A: This shouldn't be too much of a problem when the Delay has been properly set, but to set the Delay to an optimal value isn't that easy. Also there could be a problem if a packet filter stops the scan. Try to divide the range you wish to scan into several smaller, and scan them separately to minimize the effect of a possible error.

A: It means that you are running WUPS on Windows NT but you aren't a member of the Administrators group, which is required.

A: Send a mail to winnt@bahnhof.se with your question. I can't promise that I will have time to answer, but I'll do my best.

© 1999, Arne Vidström