At three o'clock in the middle of the night, I received an alert text message and got up to take a look: the number of WebSocket connections spiked to the peak, and the server CPU directly knelt. Attackers rely on WS protocol long connection characteristics, hard to drag down the business - these days, even real-time communication have to wear bulletproof vests.
Many people think that a set of CDN on everything is fine, until the WebSocket flood attack through the eyes. High-defense CDN in the end can not prevent WebSocket?I have demolished the architecture of seven vendors, directly to the conclusion: the mainstream vendors are supported, but the configuration of the pit more than enough to be able to fall dead.
WebSocket protocol itself is a “ghost”. It abandons the HTTP request-response model, and becomes a full-duplex long connection, which means that the traditional CDN caching strategy, rate limitation is almost invalid. Attackers only need to establish a connection to continue to consume server resources, the cost of DDoS is ten times lower than HTTP.
I've tested a vendor's default configuration: after turning on WebSocket support, the connection timeout is not adjusted. The attacker establishes 100,000 long connections and keeps each connection for 15 minutes, directly draining the back-end resources. If a high-defense CDN only protects against HTTP, it is equivalent to installing a vault lock on the door but leaving a dog hole.
A truly reliable protection must meet three points: protocol recognition, connection behavior control, and business logic filtering. CDN5 has done a great job in this area: it not only recognizes WS/WSS protocols, but also detects connection heartbeat packet anomalies. Last year, we were attacked by a crypto mining pool, and we relied on its traffic fingerprint library to cut off malicious connections.
The key to configuration is not as simple as checking “Enable WebSocket” on the interface. In the case of CDN07, for example, the four layers of protection must be synchronized and adjusted:
Don't believe the “smart defaults” that vendors talk about. Once I was lazy and used the default configuration directly, the result was 3000 new connection requests per second directly to the threshold. Later, I manually set the maximum number of connections per IP to 20, and the number of abnormal connections plummeted to 90%.
08Host's strategy is even more radical: it supports deep parsing of the WebSocket protocol. Not only can it detect SSL handshake anomalies, but also do content verification on WebSocket data frames. Having encountered CC attacks with transport layer encryption, its rule engine accurately discards malicious packets through load feature code matching.
Behind the price war lies a performance trap. A cheap vendor claimed “full-featured support”, the actual use of the WebSocket latency found up to 200ms. unpacking only to find that their nodes have done protocol conversion: the WS traffic into HTTP chunked response, the name of the compatibility optimization.
The real performance comparison depends on three sets of data: connection establishment delay, long connection stability, and attack interception efficiency. We have pressure tested the three Hong Kong nodes:
CDN5 first handshake average 87ms, 10,000 connections to maintain latency fluctuations ≤ 15ms; CDN07 connection faster (62ms) but anti-attack when the CPU spike is obvious; 08Host balanced and optimal, especially in the SSL offloading performance ahead of 40%.
The protection effect also depends on the actual battle. A game platform suffered a WS reflection attack, the attacker forged the source IP to send a large number of small packets. CDN5's protection strategy directly enabled rate limiting + packet length detection, and a single IP more than 50 packets per second immediately triggered the man-machine verification.
The most pitiful is the “fake protection” of some vendors: only in the TCP layer to do traffic cleaning, completely regardless of the application layer protocols, WebSocket attacks penetrate as usual, and after-sales also dumped the pot, said “business code has problems”. Later, I changed to use CDN07's seven-layer protection, and added this rule to cure it:
Business layer protection is the ultimate weapon. Last year, a financial project was attacked by WS API abuse, and the attacker simulated normal clients to send high-frequency transaction requests. In the end, CDN5's customized rules broke the game: detecting the number of requests per minute for a single connection, and forcing the connection that exceeds the threshold to disconnect and blacken the IP.
Now pick a high-defense CDN must see WebSocket protection details: whether to support the connection length limit? Can it recognize protocol disguise? Is there any business wind control linkage? A vendor can even dock the self-built wind control system, real-time issuance of interception instructions - this has been the ability of the WAF level.
On an offending note: 90%'s WebSocket protection problems stem from misconfiguration. The most outrageous incident I've seen was an engineer forgetting to turn off a test rule and blocking all legitimate connections to the production environment. It's really not that the vendor can't do it, it's that a lot of people don't even understand the console.
In the future, attacks will definitely evolve towards hybrid protocols, with WebSocket over HTTP/2 and QUIC protocol abuse already circulating in the black market. The least you can do is to make sure that the vendor updates the protection rules on a monthly basis. 08Host's threat intelligence database is updated three times a week, which is a real relief.
If you are selecting a model, remember these three ironclad rules: always press WS performance during testing, specify the protection index in the contract, and do attack and defense drills on a regular basis. Don't wait for the business to collapse before checking the documents, real-time communication protection is never a switch project, but a continuous confrontation.
WebSocket protection has long been not a question of “to do or not to do”, but a race of “how detailed to do”. Top CDNs are piling up machine learning models to dig out attack patterns from connection behavior. The next time you encounter sales bragging about million-level QPS protection, directly ask: WS long connection CC attacks can be prevented to what granularity?
Technology is ultimately a tool, the real protection lies in a deep understanding of the business logic. I still keep the habit: every online WS service, must use Slowloris, WS-Attacker tool self-test. There is no silver bullet for security, but high security CDN at least gives us the right to wear armor.
