I have been using the same computer with the same isp and firewall for quite some time now. However since the past 2 days I kepp getting atleast one alert log telling me that a fin scan is underway. It gives me the remote ip too and the network isnt even on my isp. Why is this happening so often. I am using http://www.f-secure.com/en/web/home_global
Scan your computer for backdoors, as there is a good chance some piece of malware is calling home. Malwarebytes' Anti-Malware is pretty good. Do a full scan.