It's not really a mask, it is the actual IP address converted to a code written in HEX though the format used by my ISP is probably a better one for room hosts where it simply contains CPE-147-10-19-2.
nsw.bigpond.net.au - with the full IP (falsified in this case) and a a part of the hostname dedicated to a geographic location (the bit in brown) makes life much easier.
As for AO-Hell, *!*@ACBF09*.ipt.aol.com would assist when banning a ban evader.
