What is DDOS?

DDOS, short for Distributed Denial of Service, refers to a type of cyber attack aimed at disrupting the normal functioning of a network service by overwhelming it with a flood of internet traffic. The purpose is to make the service inaccessible to legitimate users. Unlike DOS (Denial of Service), which involves a single source attacking, DDOS utilizes multiple compromised computers (zombies) to attack the target simultaneously, thus amplifying the impact.

DDoS Protection: 6 Simple Tactics（2024）

How to Determine if Your Website is Under DDOS Attack?

DDOS attacks manifest in two primary forms:

1. Traffic Attack: This involves flooding the network bandwidth with malicious traffic, causing legitimate requests to be drowned out by the attack traffic. Signs include ping timeouts or severe packet loss compared to normal conditions.

2. Resource Exhaustion Attack: This targets the server resources (such as memory or CPU), making the server unable to fulfill legitimate requests. Symptoms include slow website response or complete unavailability despite being reachable via ping.

Common Types of DDOS Attacks:

1. SYN/ACK Flood: Overwhelms servers with spoofed SYN or ACK packets, exhausting server resources.

2. TCP Connection Flood: Floods servers with TCP connection requests to exhaust their capacity to handle new connections.

3. Script Flood: Exploits scripts (ASP, JSP, PHP, etc.) to exhaust database resources with excessive queries.

How to Mitigate DDOS Attacks?

Defense against DDOS attacks requires a systematic approach:

1. High-Performance Network Equipment: Use reputable routers, switches, and firewalls to ensure they can handle high volumes of traffic without becoming bottlenecks.

2. Avoid NAT: Minimize the use of Network Address Translation (NAT) as it can degrade network performance under attack conditions.

3. Adequate Bandwidth: Ensure sufficient bandwidth to absorb and mitigate attack traffic. Higher bandwidth reduces the impact of DDOS attacks.

4. Upgrade Server Hardware: Enhance server hardware (CPU, memory, network cards) to better withstand DDOS attacks.

5. Static Website Pages: Convert dynamic pages to static where possible to reduce vulnerability to script-based attacks.

6. Enhance OS TCP/IP Stack: Optimize TCP/IP settings on server operating systems (e.g., Windows Server) to improve resistance to DDOS attacks.

7. Install DDOS Mitigation Solutions: Deploy specialized DDOS mitigation tools or services like CDN5 to protect against large-scale attacks effectively.

8. Other Defense Measures: Implement additional security measures such as rate limiting, IP blocking, and traffic filtering to mitigate DDOS attacks.

By implementing these strategies, organizations can significantly enhance their ability to mitigate DDOS attacks and maintain the availability of their online services. 

To effectively defend against CC attacks, website administrators can take the following measures:

1. Use of CDN (Content Delivery Network): CDNhelps distribute traffic and cache requests on servers worldwide, thus alleviating pressure on the target server.

2. Implement IP Restrictions and Access Control Lists (ACL): Configure firewalls or web server software to restrict requests from specific IP address ranges.

3. Deploy Web Application Firewall (WAF): WAF can detect and block malicious HTTP requests, filter out abnormal traffic, and protect the website from attacks.

4. Enhance Server Performance and Network Infrastructure: Increase bandwidth, upgrade hardware, optimize software configurations, etc., to improve server processing capabilities and stability.

5. Implement CAPTCHA Verification: Add CAPTCHA verification steps in user requests to confirm if requests originate from real users, thus blocking automated attack tools.

6. Real-time Monitoring and Response: Utilize security monitoring tools to monitor website traffic in real-time, promptly detect abnormal traffic, and take appropriate response measures.