I used to have an old ICQ IP sniffer from ICQ Team, but it no longer works. I used trillian instead, to obtain the I.P. addresses. Sometimes depeding on how secure someones connection is, with a good proxy and firewalls, the i.p. will read as: 0.0.0.0.
I wouldn't trust any ICQ I.P. sniffers anymore, since they have the potential of submitting username and passwords via another computer as a log file.
Sometimes people will use a false proxy, especially if they are a server admin, they can spoof the I.P. but ever since 9/11 Internet security in America has tightend, and new technologies have made it more difficult to accomplish these tasks.
ISP's are highly stressed on new focus rules and internet regulations for security. The FCC and the FTC enforce these policies strictly for ISPs to follow.
What pisses me off is some of these whois providers are getting paid lots of money by companies like AOL, and Earthlink to make WHOIS identification by third parties unavailable, which to me, is a violation of F.C.C. rules and conduct for internet fraud investigations.
And I.P. address is only a sitting duck, if the person behind it is dumb enough to open himself/herself up for attacks.
The WHOIS I did use was built into Symantec's security section, or you can download a good WHOIS/Traceroute pinger from ipswitch.com for the evaulation version of the IP pro pack thingy, I forgot the name of it. It used to be freeware, but now has a software trial, but it's a damn good network diagnostics utility, and I've been using the software since 1996. The guy who makes it, makes Peter Norton look like a non-nerd. Originally I used it to scare kids on battle.net by identifying their I.P. and telling them where they live to scare the shit out of them.
