Technology Forum

hi there, yesterday my brother stupidly went on a website that had a keylogging hacking thing on. he was on habbo hotel and when he clicked on it he got logged out, does this mean this hacker is already on my network? and is this stuff virus based? i was told that he can go trhough my IP address and get my host and be able to browse through our network and get confidential information which is very worrying. So we dissconnected out internet and phoned my ISP which is talk talk, they assured us that we have a dynamic IP address which keeps changing. The guy who told me about this said that if u change ur ip address this hacker will have an invalid ip address, so he couldnt do anything. Would this dynamic IP address of mine stop it? if not what should i do, if this virus is on the pc that it was downloaded to, can it spread accross my network to my other pc's? if i reformat the pc that was used to click on the link, will it stop it? please help from what ive heard this is very serious, Thankyou for your help. regards, Will B