If you have a static IP it is actually very common for "known trojan ports" to get alot of hits especially when on any p2p network.
At one time I got so many hits I simply turned off the prompts and locked everything down as tight as I could.
depending on how paranoid you are
you can create rules that block all know trojan ports which takes some time. But there are a few groups out there like Napho said that
make a lifes work out of these things. Often times you can download/view actual rule sets for your firewall to simplify the process.
Disable simply things like ping commands etc with your firewall that you may not need and easily give you away.
Buy hardware protection if you don't already..... a router is a good simple and inexpensive firewall that is very effective against random scans etc.
Remembering the whole time that
nothing is secure if someone really wants in they will probably get in.
