Ip address query ?

Question

Hello friends

Well coming to my doubt directly . lets hope i have web site with chat enabled option for users before they register to well know about the site . .! so if some one misbehaves is chat chat box with support team . .i do i.e  they do block that person ?? in this case how come they block the person ??

I think via IP address ?? is that true ?? Is so is systems in this generations provide Dynamic IP  ?? if they how come they block ??

Hope you guys gt my problem ..

Waiting for ur reply :)

Thank you