windows 7 - How to block an ip address

My sisters laptop is clogging up the router with massive amounts of connections, probably a virus of some sort but various antivirus software found nothing.

The connections are from and to 90.190.86.248 googling told me that its widely blacklisted for being a spambot but not much else.

Anyway at first i tried to deny the ip in router settings (thomson tg784) and that did nothing. Next up i set up the hosts file to point to 127.0.0.1 but that didn't do anything either. Then i set up a custom rule in windows firewall for that address and guess what, still nothing :/

I really don't have the time to deal with this properly right now, any ideas on what kind of bandaid to use?

Try to isolate computer firewall (Windows Firewall Advanced Settings, and Connection Options or something like that). Then select isolate, and then first option (Request Connection Authentication). Most known websites will work, but not, for example virtualbox.com. If she plays like "WoW" or something, you can add all WoW's IPs to firewall (if you are PRO). ALTERNATIVELY: Get zonealarm firewall + antivirus free, and the listening ports wont do any harm, but it probably wont work for all threats.

Myself Im paranoid against viruses, so Im isolating all websites and allowing only a few. (This works too, but its painful to add all websites one by one).