Protect game servers from UDP floods: traffic scrubbing, proxy, closing ports, rate limiting, and contacting your hosting provider.
The fastest way to stop a UDP flood against a game server is always-on scrubbing or a proxy at the network edge. Local firewall rules complement this protection but do not replace it, because the server itself has hardly any capacity to withstand millions of packets per second. Rate limits on the target port, closing unnecessary ports, and contacting the hosting provider directly also help immediately. This order matches the recommendations of the BSI on protection against DDoS attacks.
In short:
- With UDP floods, quickly activating always-on scrubbing or a proxy at the network edge is crucial to filter the data stream effectively.
- Attackers often send much larger packets than legitimate users, which greatly increases the volume of attacks on game servers and puts heavy load on the CPU.
- Clear threshold monitoring enables early detection of attacks based on sudden, rapid traffic increases, source diversity, and unusual packet sizes.
- Local firewalls offer only limited protection, while network-side filtering by the provider and cloud protection provide long-term security.
- Automated emergency measures, such as combining edge rate limits with cloud scrubbing, minimize downtime and make it easier to fend off large volumetric attacks.
When players suddenly report lag and the network graph shoots straight up, every second counts. Stay calm, then work through it systematically:
Pro tip: Keep a prepared ip6tables or mutable rule at hand that you can activate with a script in seconds, instead of writing it from scratch under stress.
UDP is connectionless: there is no handshake in which the sender would have to prove it is genuine. Attackers take advantage of exactly this. In normal operation, a game server handles a certain pattern of packets per second (PPS) and bytes per second (BPS), which varies significantly depending on the game.
Statistic: According to analyses, UDP flood attacks frequently reach 200,000 to 500,000 packets per second, many times the legitimate server load. The kernel has to process every single packet before it can drop it, and it is exactly this processing step that eats up the CPU.
Without a clean baseline, it is hard to tell an attack from a sudden rush of players. A multi-level threshold system that takes a port's normal value as its starting point is a sensible approach.
Automatic mitigation is mainly worthwhile at critical thresholds, whereas warning levels deserve manual review, otherwise you end up blocking a streamer-driven rush that was not an attack at all.
No single building block solves the problem completely; each layer has its role.
Pro tip: Combine local rate limits with an always-on solution: the firewall absorbs smaller spikes, and scrubbing takes over for genuine large-scale attacks.
An attack unfolds in phases, and each phase needs a different response.
Practical examples show that combining FlowSpec rules at the edge with temporary cloud diversion resolves many incidents with only brief player impact, and the diversion is rolled back automatically once the attack subsides.
| Phase | Time window | Main action |
|---|---|---|
| A | 0 to 10 seconds | Confirm alert, initial block rules |
| B | 10 seconds to 5 minutes | Edge rate limits, provider contact |
| C | from 5 minutes | Cloud scrubbing, IP rotation, analysis |
The best incident is the one that never escalates. A proxy or edge architecture hides the real server IP from the start, so attackers do not even know where to send their packets. Restrictive port policies, where only the absolute minimum stays open, reduce both the attack surface and the administrative effort.
A guide to data protection and hosting is also worth a look, because incident response and compliance are more closely linked than many operators assume when it comes to personal data on game servers.
Pro tip: Test your setup with an announced internal load scenario before the first real attack shows where the weaknesses are.
Recent reports on the DDoS landscape describe rising attack volumes and increasingly complex attack patterns; one trade article describes DDoS attacks as now being as commonplace as the weather. This argues for treating always-on protection as the standard rather than as an emergency reaction. Some hosting providers offer game servers, VPS, and dedicated servers with integrated DDoS protection at no additional cost. For operators who cannot build their own round-the-clock network monitoring team, a hosted solution with integrated protection is often the more realistic option than a pure DIY setup.
— Erik
If you prefer protected infrastructure, various providers offer options with integrated DDoS protection that may be included with their server products.
If you are unsure which configuration suits your type of players, you can clarify your needs directly with support and choose the right solution.
A UDP flood overwhelms a server with packets over the connectionless UDP protocol, and the sender is often spoofed. Game servers are especially vulnerable because they already process many small packets per second, and an attack exceeds that load many times over with much larger packets, as analyses of current attack patterns show.
A local firewall helps with smaller spikes and closes unnecessary ports, but it quickly reaches its capacity limit in large attacks. For reliable protection, the BSI (German Federal Office for Information Security) additionally recommends network-side filtering and qualified service providers.
A real attack shows a very fast ramp rate, meaning an increase within seconds rather than minutes, and often a high number of different source addresses. Thresholds such as three, five, or ten times the normal baseline, as described in playbooks for game hosting, help tell the two apart.
Some hosting providers offer game servers, VPS, and dedicated servers with integrated DDoS protection, which can relieve operators compared with managing rate limits and scrubbing entirely on their own. This is a practical complement to the immediate measures described in this article, especially for operators without their own network team.