Defending Game Servers Against Layer 7 DDoS Attacks
Go beyond basic DDoS protection. Understand how Layer 7 attacks target game protocols (A2S_INFO) and how we filter them.
When most people think of a DDoS attack, they imagine a massive volumetric flood (Layer 3/4) that simply fills up a server's internet pipe. However, modern attackers targeting game servers use much more sophisticated Layer 7 (Application Layer) attacks.
The A2S_INFO Exploit
In games using the Source engine (CS 1.6, CS2, Rust, GMod), the server browser pings the server using an A2S_INFO query to ask for the server name, map, and player count. The server responds with a data packet.
Attackers realized that by sending millions of spoofed A2S_INFO queries, they force the game server CPU to process the request and formulate a response. The network isn't clogged, but the CPU hits 100%, causing the server TPS to plummet and players to time out. This is a classic Layer 7 attack.
How GameSphere Filters Layer 7
Generic DDoS protection (like standard Cloudflare or Arbor) cannot stop this, because to a generic firewall, an A2S_INFO packet looks like legitimate game traffic. If the firewall drops it, your server disappears from the in-game server list!
GameSphere utilizes deep packet inspection and stateful UDP tracking:
- Query Limiting: We track the rate of queries from specific IPs and instantly block excessive polling.
- Challenge-Response (Cookies): During an attack, our edge filters intercept queries and force the client to complete a lightweight cryptographic challenge. Legitimate game clients pass automatically; botnets fail and are dropped at the edge, saving your server's CPU.
This ensures your server remains visible in the master server list, while rendering application-layer attacks completely useless.