DDOS (distributed refusal service) attack is a malicious method of attack, which aims to make the target website or network resources work properly, resulting in unavailable services. Here are some methods of DDOS defense:

　　1. Use DDOS defense software. Many security suppliers provide specialized DDOS defense tools that can help identify and separate malicious traffic and ensure that only legal data requests can reach the target server.

　　2. Load balancer. The load balancer can distribute the access request balance to different servers to ensure that the flow is dispersed and reduced the risk of a single server to suffer from DDOS attacks.

　　3. Cloud service provider. Many cloud service providers provide highly scalable and flexible infrastructure, which can help defensive DDOS attacks.

　　4. Limit IP access. You can build the number of IP addresses connected to your target server, which can limit the impact of DDOS attacks.

　　5.CDN service. CDN (content distribution network) service provides a cache technology that can mirror your contents on multiple servers and predict possible IP sources. This can help reduce the impact of DDOS attacks.

　　In general, the DDOS attack is a serious network security threat that needs to adopt various methods to protect your network system.