Solution to attacks abusing connection packets?

Note: Sorry if I am not giving enough information, I don’t know much about networking.

My server has been offline for around 3 days so far, the information I have from my host (NFOServers) is that the packet they are spamming is a “connection packet” so blocking it would block legit traffic also so that isn’t much of a solution.

It’s been 3 days and I really would like to find a solution, the game server is Garry’s Mod.

Packet example from wireshark capture:

Any help you can provide is much appreciated.

This seems more like a server issue rather than a Garry’s Mod issue, probably better in technical support. As for a solution I myself am not very experiencing in networking. If the spam is coming from 1 or 1 group of IP addresses then you should be able to block that, if it’s completely random maybe try your server on a different port, although I’m not sure how much this will help

The IPs are spoofed so blocking IPs is not an option, whoever is responsible is also watching for my server, I have started it on 5 different ports and multiple IPs and it gets hit by the same sort of attack.

Did you fix it? I am having the same problem.