In the end, people who have fun by reducing the fun of others are bad people. Good people have fun by increasing the fun others have.

@ DC: For me there's no need to imagine what gonna happen if I were a server owner, I have own servers in this game and I pay for them. But I still can't understand, why this bug with null UDP packages is not fixed? You know about it and other people (for example, me) knows about it too. Things like "dudes, don't crash servers, please" is extremely low effective in comparison with bug fixes.

I can see that this bug has been described in 2015: http://web.archive.org/web/20150922053506/http://www.cs2d.com/security.php. Is it hard to find a solution during 6 years? If you are so worried about the multiplayer in game, why you did nothing more than just wrote this article? This article did some "negative" effect for the multiplayer mode, because I understood that this bug exists only after I've read about how to protect servers from empty UDP packages.

It may seem that I was doing this just to destroy the competition servers. But I was doing it really just for fun. But sending empty UDP packages is not a hard thing, so any "bad guy" can use software like https://packetsender.com/ to crash servers via bug which was described on cs2d.com in 2015.

@ mrc: did people leave because of DoS attacks? I started playing this game since later 00s and I haven't see a lot of DoS attacks. If DoS attacks did run the game, why do we have more servers than players?

CS2D is a casual game. Casual games are made for fun and people doesn't spend a lot of time playing it. This is what we can see in Steam: a lot of reviews, good and bad, are writen by players who spent just several hours in this game. People who are active in CS2D for several years (like you and me) are an exception and the real fans of the casual game.

People who left this game after several years playing it, most likely just got bored and tired from CS2D. And I can understand them: they just found new interests.

@ ohaz: what can be determined as reducing the fun of others? Some players may feel unhappy if they got killed by someone, if the server is lagging, if one of teams is full, if server doesn't registers damage and other things. In this case, what can we describe as increasing the fun others have?

From the side of DoS attackers: can server owners who does protect their servers be described as bad people? Because server protection ruins the fun for them. But I can call you a good dude because you increased the fun for me when you mentioned the law.

@ Kolia_rus: Unfortunately I failed to fix it and I'm running out of ideas what I can try. Of course this would be the most efficient solution. It would be even easier though if people would just stop doing this bullsh*t for no reason - and yes, I'm aware that this will never happen.

@ DC: Wouldn't just having a proxy receiver for all UDP packages that ignores empty packets solve it?

@ DC: I think that if you can't fix it, it would be good if there will be a warning like "It seems like you've not set the server protection correctly. Come read: cs2d.com/security.php", which will be automatically displayed if commands from this page have unsafe values. I am not an experienced Linux user, but I think there will be no problems if the dedicated server will execute the iptables -A INPUT -p udp -m length --length 0:28 -j DROP command on launch.

And the solution to tell all people that they should just stop crashing servers is impossible. There is a some kind of passion in using bugs for such people as me.

I like how people think it just that easy... IPTables would only handle weak attacks, normally you would need something like OVH with a DDoS protection that does anything effective.

If setting things would be just matter of money and solution, companies like Facebook and so on wouldn't have the same problem.

If DDOSing is that easy, then I understand why people would do it.
Anyway - on the topic, I'm not sure what you could do to protect your server, I don't really see any good options on how to protect your server, so I think you should put in some basic protection and yeah

Nobody attacks CS2D servers with more than 1GB/s attacks, it's just too expensive, and would be a lot easier to get in trouble for.