Xmas port scan

Is anyone else suffering from slow/stopped broadband due to continous "Xmas port scan attack from WAN(ip address)"

This seems to have slowed our service at times to a crawl but although I have registered a fault all I get offered is line checks.

I get occasional slow or stopped BB, but how would I know it was due to "Xmas port scan attack from WAN(ip address)"? I use Linux BTW.

Disable any sort of port scanning/denial of service "protection". It's a waste of CPU cycles.