The attack is based on exploit of RakNet bug, on which all master list of SA:MP is running...
Right now we do see only one way of stopping the attack on our main server... That will take a time, as the attack is not a usual DDOS attack... I personally hardly see any other ways to stop attack even with software security due to RakNet system of pinging the servers... As software security can affect on normal players as well...
Attack is going only on one Argonath server... All others were down due to our testing and checking the software security running...
So please be patient and admins please continue your work...
It has also the good side for us as experience with the master list running and its possible problems which showed RakNet system for example, which is good for our own developing...

It will prevent us from DDOS attacks of new game servers in master list by exploit of pinging the servers...