How can you learn IPs of the users (tested with only ICQ98)
If users check Security & Privacy / Security / IP Hidding box we can't see their IP nnumbers. But with a small trick we can see althogh they check Security & Privacy / Security / IP Hidding box. Process the steps and enjoy :

 

1- Look at someone's "Info". As you see its IP is hidden. It says "N/A".

2- Now go Offline/Disconnected.

3- Now look at the same "info" box and you'll see its IP.

 

How can we prevent being harmed:
1-
Look at the "Define your IP yourself" section.
2-
Add the people you don't know to your invisible list and don't authorize people you don't trust.