I remember last year there was a social platform, because the CC attack directly to the comment system dry down, I was as a member of the emergency response, was called up in the middle of the night, watched the monitoring charts like a roller coaster soared, the server load instantly burst the table, that scene is really acidic.
What's the big deal about this CC attack? It's just a lot of requests, isn't it? But really encountered to know, it specializes in picking the soft underbelly of the fight - such as message comment interface, which is a place of frequent user interaction, database read and write more, once the flood of false requests inundated, the response is slow, or the entire service is down, the user curses the small matter, the brand credibility of the smashed is the real end of the game.
I found that a lot of teams thought on the CDN on the high pillow worry-free, the results of the CC attack came, the CDN first kneel - because the configuration did not do fine, the traffic did not filter clean, but became an accomplice. These days, even the CDN have to ‘defense teammates‘, do not believe that those 'one-key protection' of the ghost words, accurate defense have to do it yourself.
The root of the problem lies in the fact that CC attacks simulate real user behavior, such as high-frequency comment submission and page refreshing, and traditional firewalls may mistakenly kill normal traffic, while ordinary CDN caching strategies can't block dynamic requests. Message comment interfaces are usually API endpoints such as/api/comments/postThe attackers use botnet to send crazy POST requests, each with a bit of garbage data, the server just to process these on the CPU soared full, the database connection pool is taken up, the normal user naturally jammed.
For example, once I helped a social app to do an audit, their comment interface did not limit the speed, a minute the same IP can send hundreds of comments, the results were hacked with a proxy IP pool wild brush, the peak QPS (queries per second) rushed to 100,000 +, the server directly 503. Looking at the logs after the fact, most of the requests User-Agent are forged, the source IP all over the world, but Pattern is very consistent - short intervals, small packets, clear purpose.
So the solution has to be layered: first rely on the CDN to carry most of the traffic, and then the back-end to do the fine rules.CDN selection is the key, I've compared a few - CDN5 in the intelligent caching and elasticity of the expansion of the bull, especially suitable for unexpected traffic; CDN07 WAF (Web Application Firewall) rule base is updated quickly, can be automatically identified CC features; 08Host cost-effective and flexible custom rules for teams with tight budgets. automatically identify CC features; 08Host cost-effective, flexible customization rules, suitable for teams with tight budgets. But no matter who you choose, the configuration has to be hand-tuned.
The first step is to set Rate Limiting in the CDN management console. For example, for/api/comments/**The path, set a single IP up to 5 requests per second, beyond the return 429 status code. CDN5's configuration interface is intuitive, I often set this:
Never set too strict, otherwise real users will be mistakenly hurt if they post comments faster - I've stepped on this pit, once the threshold was set to 3, and as a result, when the event was held, users were wildly praising, and normal requests were blocked, and the complaint phone number was busted. Later, I learned my lesson and dynamically adjusted it in conjunction with the IP reputation repository.
The second step is to enable the CAPTCHA challenge. For suspicious traffic, such as a large number of requests from the same IP for a short period of time, the first pop-up CAPTCHA to slow down the pace of the attack. CDN07 supports this feature, the configuration of the attention not to affect the user experience: only POST requests take effect, the GET request (such as reading comments) release. Code example:
I've tested it and found that it can take out 90%'s easy CC attack, but advanced attacks will use OCR to crack the CAPTCHA, so it has to be paired with other means.
The third step is IP blacklisting and geo-blocking. CC attacks commonly use cloud hosts or proxy IPs, and the blacklist is updated in real time through threat intelligence sources such as AbuseIPDB. 08Host allows uploading of customized IP lists, and I wrote a script to synchronize them on a regular basis:
Geo-blocking is also quite useful - if the business only serves domestic, block overseas IPs directly. but beware of accidentally killing VPN users, it's best to leave a whitelisted channel.
The fourth step, cache strategy optimization. Static resources (such as avatars, CSS) cache longer, dynamic interfaces (such as comment submission) set a short cache or disable cache, forcing the traffic to go WAF detection. cdn5 cache rules can be so matched:
This way every comment request goes back to the source for detection, which increases latency but safety first. I suggest using asynchronous processing - users send comments first return success, the background queue processing, to reduce real-time pressure.
The fifth step is to reinforce the back-end; CDNs are not silver bullets, and ultimately the defense has to come back to the servers; add a flow-limiting module to the Nginx layer, e.g., with thelimit_req_zone：
This rule means that the maximum number of requests per IP per second is 5, the burst is allowed to be 10, beyond the direct 503. burst parameter should not be set indiscriminately - I once set it too large, the attack came to the queue backlog, the memory blew up. Combined with log monitoring, real-time adjustment.
Finally, monitoring and response. Set alert rules: SMS notification when QPS surge, 5xx error rate exceeded. Tools such as Prometheus+Grafana, Kanban configuration example:
Don't wait for things to go wrong before checking - do a weekly attack and defense drill to simulate a CC attack to test the effectiveness of the defense. My team does this all the time, finding a point in time to scrub the interface and see if the rules are triggered.
In short, social high-defense CDN configuration is not a once-and-for-all job, you have to continue to iterate. CDN5, CDN07, 08Host each has its own style, but the core idea is the same: layered defense, fine rules, real-time monitoring. Remember, security is a process, not a product. User reviews are small, behind the trust system, smashed and then repair can be difficult.
Act now: check your CDN configuration...is the rate limit set?...is the IP blacklist updated? If you haven't done so, hackers may come to ‘greet' you tonight. Feel free to leave a comment if you have any questions - don't let the comment interface become a disaster area.
