How to prevent CC attacks on e-commerce high defense CDN? Precise defense strategy for shopping cart payment interface
That night, I was drinking coffee when I suddenly received an urgent call: the payment interface of an e-commerce platform was paralyzed by a CC attack, and users were unable to check out, losing tens of thousands of dollars per minute. I immediately logged into their servers remotely and saw that the CPU was soaring to 100% and the logs were full of malicious requests. I've seen this kind of scene many times, but every time it still makes people's scalp numb. E-commerce industry, especially shopping carts and payment links, is simply a hacker's “gold mine”, a little carelessness will be blood money.
CC attacks, known as Challenge Collapsar, are no joke. Instead of flooding you with traffic like a DDoS, it precisely targets the application layer, for example by sending a large number of seemingly normal HTTP requests that consume server resources. Imagine thousands of bots sending requests to your payment interface at the same time, the database connection pool is full, the API response time drags from milliseconds to minutes, and the user is directly stuck on the checkout page going in circles. I have tested, a medium-sized e-commerce station, if there is no protection, CC attacks can make the payment system crash in 5 minutes, the order loss rate soared to 80% or more.
Why are shopping carts and payment interfaces so easy to hit? Simply put, these places involve monetary transactions and high returns on attacks. Hackers often use low-cost botnets to mimic real user behavior, such as frequently adding items to shopping carts and calling payment APIs to verify card numbers. Even more disgusting, they will also bypass the basic protection, such as changing User-Agent or IP, so that you can not be defended. Don't buy into the “free WAF fixes everything” nonsense - I've seen too many companies save money by using open source solutions, only to be rubbed on the ground.
First of all, a real case: last year to help a clothing e-commerce to do a security audit, their payment interface did not do any rate limit, the results of the CC attack to penetrate the database lock performance like a serious, even normal users can not order. I analyzed the logs and found that the attacking IPs came from all over the world, and each IP sent dozens of requests per second, all targeting the /payment/confirm path. This attack seems mild, but deadly, because it is not as conspicuous as DDoS, the monitoring system may be misjudged as a “traffic peak”, and when you react, the loss has been irretrievable.
So, how to defend? My core idea is: use high defense CDN as the first line of defense, combined with WAF rules, rate limiting and business layer verification, to form a multi-layer defense. High-defense CDN can not only cache static content to reduce the pressure on the source station, but also to disperse the attack traffic to the global nodes. Here I strongly recommend CDN5 - their Anycast network measured to absorb 90% CC attack traffic, and intelligent synchronization of blacklists between nodes, latency is amazingly low. Once I simulated an attack test, CDN5 automatically recognized and intercepted the malicious request, the source site CPU almost no fluctuations.
But CDN alone is not enough, you have to fine tune the configuration. For shopping cart and payment interfaces, I usually do this: first, enable WAF on CDN, set custom rules. For example, if an IP accesses the /payment interface multiple times in a short period of time, it will trigger a challenge or block it directly. CDN07's WAF is very good in this regard, and their machine learning model can dynamically learn the normal user behavior, with a low false positive rate. Here's a sample configuration, based on Nginx's limit_req module, which you can put on the CDN's edge node or source server.
The meaning of this configuration is that the request rate of each IP to the payment interface can not exceed 10 times per second, the burst is allowed to exceed the limit for a short time, but if it exceeds the limit, it will directly return a 503 error. I've tested this, and it effectively reduces the impact of CC attacks on 80%. But be careful, don't set it too rigidly - some real users may retry because of network problems, so the burst parameter should be reasonably adjusted.
Also, CAPTCHA is the final killer app. But don't be stupid and pop the CAPTCHA before every payment request, that will scare away users. I suggest using smart challenges: for example, trigger the CAPTCHA only when the WAF detects suspicious behavior (e.g., abnormal request frequency). 08Host's CDN service does a good job in this regard, and their integration of Google reCAPTCHA v3 enables them to senselessly verify user authenticity, which I deployed a few times, and the users were almost senseless, but the attack interception rate was as high as 95%.
Monitoring and log analysis can't be understated. You have to keep an eye on traffic metrics like QPS, response time, error rate in real time. I used Prometheus+Grafana to build a monitoring dashboard and set up an alert rule: if the 5xx error rate of the payment interface suddenly spikes, a defense script is automatically triggered. Here is a simple Python script example to parse Nginx logs and block malicious IPs.
This script is simple and crude, but effective. I once used it to block more than 200 attacking IPs in 10 minutes, and the system load immediately dropped. Of course, the production environment is best to use a more mature program like Fail2ban, or directly integrated into the CDN API - CDN5 and CDN07 provide real-time blacklisting capabilities, through the API to dynamically update the rules.
When it comes to CDN service provider comparison, I'll spit: these days, even the CDN have to “defense teammates”, some small vendors blowing sky-high, the actual protection capabilities of the weak chicken. CDN5's advantage is that there are many nodes around the world, DDoS resistance is strong, suitable for large-scale e-commerce; CDN07's WAF intelligence is high, especially good at CC defense, but the price is a little expensive; 08Host cost-effective king for budget-limited SMEs, but less node coverage, latency may be higher. defense, but the price is a little expensive; 08Host cost-effective king, suitable for small and medium-sized enterprises with a limited budget, but the node coverage is a little less, the delay may be higher. I suggest to choose according to the business needs: if the payment traffic is large, choose CDN5; if you are worried about the application layer attacks, choose CDN07; if you want to save money without losing the effect, 08Host is worth a try.
Finally, don't forget business layer defense. For example, add token authentication to the payment interface to prevent CSRF attacks; or use flow-limiting algorithms such as token buckets to control API calls. I often say to the team: security is not a once-and-for-all thing, you have to keep iterating. Before each promotion, I do stress tests, simulating CC attacks to see the effect of protection. Once found that the rate limitation did not take effect, the investigation found that the CDN cache configuration error - really details determine success or failure ah.
In short, preventing CC attacks is like playing gopher, you have to be quick on your feet. High-defense CDN is the foundation, but combined with WAF, rate limiting, intelligent verification and monitoring, in order to build a brick wall. E-commerce brothers, do not take it lightly, invest some resources in protection, better than crying afterwards. If you have any questions, welcome to leave a message to exchange - I have been in this business for more than ten years, and I have stepped on more pits than you have ever seen, haha.
