Perimeter firewalls help prevent DDoS (Distributed Denial of Service) attacks by acting as the first line of defense between an organization's internal network and external threats. They monitor, filter, and control incoming and outgoing network traffic based on predetermined security rules. When a DDoS attack occurs—where multiple compromised systems flood a target with excessive traffic—a perimeter firewall can identify abnormal traffic patterns and block or throttle malicious requests before they reach critical internal systems.
Here’s how perimeter firewalls mitigate DDoS attacks:
Traffic Filtering: Firewalls can be configured to allow only legitimate traffic based on IP addresses, ports, protocols, or packet content. During a DDoS attack, they can block traffic from known malicious IP ranges or suspicious patterns.
Rate Limiting: Firewalls can limit the number of requests a single IP address can make within a certain timeframe. This helps prevent an overwhelming number of requests from a single source or botnet.
Connection Limits: By restricting the number of simultaneous connections from a single IP or to a specific service, firewalls can reduce the impact of connection-based DDoS attacks like SYN floods.
Signature and Anomaly Detection: Advanced firewalls may include intrusion prevention systems (IPS) that use known attack signatures or detect unusual traffic behavior to identify and block DDoS attempts.
Example: Suppose a company hosts an e-commerce website that suddenly experiences a spike in traffic from thousands of IP addresses, causing the web servers to slow down or crash. The perimeter firewall analyzes the incoming traffic and detects that a large portion is coming from suspicious sources with unusual request patterns. It automatically blocks those IP addresses and limits the request rate from others, allowing legitimate users to access the site while mitigating the DDoS attack.
For enhanced DDoS protection, especially at scale, organizations can use Tencent Cloud's Anti-DDoS services, such as Anti-DDoS Pro or Anti-DDoS Advanced. These services integrate with perimeter defenses to provide advanced traffic cleaning, real-time mitigation, and global traffic distribution to keep services online during large-scale attacks.