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The FortiGate Distributed Denial of Service (DDoS) mitigation mechanism uses a multi-layered strategy to detect and prevent malicious traffic from overwhelming network resources. Below is an overview of its key components and how they work together:
1. Behavior-Based Detection
- Baseline Establishment: FortiGate continuously monitors network traffic to establish a baseline of normal behavior. This includes metrics such as traffic volume, packet rates, session counts, and protocol usage.
- Anomaly Detection: Once a baseline is in place, FortiGate analyzes traffic for deviations, such as sudden spikes, unusual packet types, or unexpected protocol behavior—common indicators of a DDoS attack.
- Machine Learning: Advanced machine learning algorithms enhance behavioral analysis, enabling FortiGate to adapt to evolving threats and detect zero-day attacks.
2. Granular Packet Inspection
- FortiGate performs deep packet inspection, analyzing both headers and payloads to detect sophisticated application-layer attacks that may resemble legitimate traffic.
- It inspects traffic across Layers 3, 4, and 7 of the OSI model, offering comprehensive visibility into network behavior.
3. Rate Limiting and Thresholds
- Administrators can define thresholds for traffic metrics such as packets per second or connection attempts, tailored to specific sources, destinations, or services.
- When thresholds are exceeded, FortiGate applies rate limiting to prevent resource exhaustion.
4. Connection and Session Management
- SYN Flood Protection: Techniques like SYN cookies are used to defend against SYN flood attacks that attempt to exhaust server resources.
- Connection Limits: Limits can be set on concurrent connections from specific sources or to specific destinations to prevent overload.
- Aggressive Aging: Inactive or suspicious connections can be aged out quickly to free up resources during an attack.
5. Reputation-Based Filtering
- IP Reputation: Integration with FortiGuard services enables blocking of traffic from known malicious IP addresses or botnet sources.
- Geo-location Blocking: Policies can restrict or block traffic from regions commonly associated with attack origins.
6. Attack Mitigation Actions
When a DDoS attack is detected, FortiGate can respond with several mitigation strategies:
- Blocking: Malicious IPs or traffic flows can be blocked temporarily or permanently.
- Quarantine: Suspicious sources can be isolated to limit their impact.
- Traffic Shaping: Legitimate traffic is prioritized, while suspicious traffic is throttled or dropped.
- Redirection: In advanced setups, traffic can be redirected to upstream devices or cloud-based scrubbing centers for further analysis and mitigation.
7. Specialized DDoS Protection Profiles and Policies
- Custom Anti-DDoS profiles can be created for different services and attack vectors.
- These profiles are applied through firewall policies to protect specific network segments or assets.
8. DNS Protection
- FortiGate includes features to defend against DNS-based DDoS attacks, such as query floods and amplification attacks.
- It inspects DNS traffic and applies rate limiting and anomaly detection to safeguard DNS services.
9. Integration with Fortinet Security Fabric
- FortiGate shares threat intelligence and coordinates responses with other Fortinet devices, creating a unified and adaptive defense system.
In summary, FortiGate’s DDoS mitigation is a robust, adaptive system that combines behavioral analytics, deep inspection, rate control, reputation intelligence, and coordinated mitigation to defend against a wide range of DDoS threats. Its emphasis on early anomaly detection enables effective responses to both known and emerging attacks.