XMAS scan in Router Log what to do?

Everyday I check my router log and I always see someone has been trying to map my network and scan my ports. It appears as xmas scan. Should I be worried, if the router logs it does it mean it's blocked? Is there any way I can prevent this? How much am I at risk? Are there any offensive measures I can take?

Someone said I should enable "block WAN request" what does that do? Interestingly enough when I was browsing the log it said "block WAN request disabled" , as if an outside source disable it in my router.

I'm not sure if it's the same I.P, but I will be saving the logs each day and compare IP addresses. Not that it matters, as I'm sure the perp is spoofing his IP anyways.

I have a D-Link wbr-1310 and have avast internet security running.

Thanks

I use the wifi for a laptop. While my other 2 other desktop is connected with cat 5 cable.

What router are you using, some routers allow better filtering of scans, ports, etc... I have a Buffalo WHR-G54S running DD-WRT (3rd party firmware based on linux). It allows me much finer control at blocking (or allowing) inbound or outbound traffic.

It's probably Windows (or the router) polling the devices on you network.

See here: Secrets of Network Cartography - The Xmas Tree Scan (-sX)