Uhh, Actually I dont understand your words. I assumed that you're sharing your folder in the network? By sharing your folder, the only security you can get by using firewall. Try to get zone alarm or any anti-virus with build in firewall. Such as Kaspersky internet security. By deleting cookies &cache you just preventing the ad ware from infecting your computer by using browser. Simple as that. Maybe you should try using Firefox + Few Plugins (Get AdBlock Plus + Adblock Filterset.G Updater). Hope that helps.