1.Overview
A CC (Challenge Collapsar) attack is a common and dangerous type of Distributed Denial of Service (DDoS) attack. In a CC attack, attackers simulate normal user requests in large volumes, continuously consuming the target server's resources, causing it to be unable to effectively respond to legitimate user requests. It's like opening a supermarket where a large number of people flood in, pretending to shop, but never actually buying anything. A DDoS attack is more direct, flooding the system with traffic and causing it to crash. Therefore, we need to implement effective defense measures against CC attacks to ensure the stability and proper functioning of servers.
2.Limit Request Frequency
A key characteristic of CC attacks is the large volume of requests, often originating from the same IP address or user. Without any restrictions, these requests can overwhelm the server, causing it to become unresponsive. To counter this, we can set a maximum number of requests per IP address within a specific time frame. If an IP exceeds this threshold, their access will be denied. This not only helps block the attacker's request volume but also ensures the server's resources are used efficiently, significantly reducing the risk of CC attacks.
3.Captcha Protection
Implementing captchas (e.g., image or slide captchas) on critical pages and operations involving sensitive information is an effective protection measure. Captchas are designed to distinguish between human users and automated requests, which is especially useful against the automated tools often used in CC attacks. By requiring users to solve a simple captcha when accessing or submitting forms, we can block a large number of malicious requests from bots and scripts, ensuring that only real users can perform actions.
4.JavaScript Validation
In addition to traditional captcha methods, embedding JavaScript validation can also effectively reduce the success rate of CC attacks. By requiring the client to execute specific JavaScript code, the server can verify if the request is initiated by a real user. Most automated attack tools cannot execute such complex JavaScript code, so this verification method filters out a significant portion of malicious requests, improving the website’s security.
5.Real-timeTraffic Monitoring
Defending against CC attacks is not just about implementing pre-set rules but also requires continuous traffic monitoring. Using traffic analysis tools, we can track user behavior in real time and detect any anomalies. Once unusual traffic patterns are identified, quick responses can be taken, such as shutting down, restarting the system, or changing passwords. Temporary measures like limiting traffic or blocking the source of the attack can be applied to minimize the impact. With precise traffic analysis, the effects of CC attacks on the website can be effectively reduced.
6.Deploying Firewalls
A Web Application Firewall (WAF) is one of the most important tools for defending against CC attacks. It can filter malicious requests using custom rules and strategies. A WAF automatically detects typical CC attack characteristics and blocks malicious traffic. It can identify high-frequency, high-volume requests and take automated actions like IP blacklisting, identifying malicious URLs, or conducting deep packet inspection of requests to provide strong protection.
7.Implement IP Blocking
By implementing IP blacklists and whitelists, website administrators can control request origins more precisely. If certain IPs are found to be frequently sending malicious requests, they can be added to a blacklist, effectively blocking them. On the other hand, a whitelist allows pre-verified, legitimate IPs to access the site directly, reducing unnecessary server load. Precise IP filtering can not only block large-scale attack traffic but also ensure that legitimate users have a smooth experience.
8.Utilize CDN and Reverse Proxies to Offload Traffic
CDN (Content Delivery Network) and reverse proxy services play a crucial role in mitigating large-scale attacks. A CDN deploys multiple nodes around the globe, distributing user requests to different servers. This way, even if one node is under attack, other nodes can continue to serve the traffic, effectively dispersing attack traffic and relieving the load on a single server. A reverse proxy acts as an intermediary between the front-end and back-end, receiving and forwarding requests. It can also filter out some malicious traffic, protecting the back-end server from direct exposure to attackers.
I recommend using a high-defense self-built CDN—99CDN.
9.Ongoing Updates and Optimizations
A key aspect of defending against CC attacks is continually updating and refining your defense measures. Attackers are always developing new tactics, so your defense system must stay flexible and adapt to these changes. Regularly review existing defense measures, add new detection rules, update WAF protection strategies, and stay informed about emerging attack trends. This ensures the defense system remains effective and capable of countering new types of CC attacks.
10.Conclusion
Defending against CC attacks requires a comprehensive approach that combines multiple protection techniques. From limiting request rates, using captchas and JavaScript validation, deploying WAFs, to leveraging CDNs and reverse proxies, and even regularly updating your defense strategies, all these measures are indispensable. Strengthening security defenses not only prevents CC attacks from succeeding but also enhances overall service stability and user experience.