help how make iptables for bloc dos attacker

[thxyou]

hi and sorry for my bad english
pls help me how make iptables in linux ubuntu
i find this

Code:

iptables -A INPUT -p udp --dport 27015 -m length --length 28 -j DROP

27015 this my srcds port
is all what i need to stop dos attacker or what

but if the attacker atack me with random port ex: 20000 or 81 or 12345 ...
he can lag my server ?

what i need to do pls help me iam new in Linux

[BehaartesEtwas]

you need to create those rules for every srcds server port you have. in case you only have one server running at 27015, this rule alone is enough. this "DoS" attack is actually not a DoS attack in the classical sense, as it aims only to a vulnerability in the srcds server. a real DoS attack cannot be prevented my any means on the root server itself (as it simply overloads the connection of your server).

[zhelev81]

But real DoS attack needs many pc's to flood that pc so not every kid has the ability to do it