TP-Link T1600G-28PS Jetstream Smart Switches User Guide - Page 843

Configuring DoS Defend DoS Defend Configuration NULL Scan SYN sPort less 1024 Blat Attack Ping Flooding SYN/SYN-ACK Flooding WinNuke Attack Ping of Death Smurf Attack 3) Click Apply. The attacker sends the illegal packet with its TCP index and all the control fields set to 0. During the TCP connection and data transmission, the packets with all control fields set to 0 are considered illegal. The attacker sends the illegal packet with its TCP SYN field set to 1 and source port smaller than 1024. The attacker sends the illegal packet with the same source port and destination port on Layer 4 and with its URG field set to 1. Similar to the Land Attack, the system performance of the attacked host is reduced because the Host circularly attempts to build a connection with the attacker. The attacker floods the destination system with Ping packets, creating a broadcast storm that makes it impossible for the system to respond to legal communication. The attacker uses a fake IP address to send TCP request packets to the server. Upon receiving the request packets, the server responds with SYN-ACK packets. Since the IP address is fake, no response will be returned. The server will keep on sending SYN-ACK packets. If the attacker sends overflowing fake request packets, the network resource will be occupied maliciously and the requests of the legal clients will be denied. Because the Operation System with bugs cannot correctly process the URG (Urgent Pointer) of TCP packets, the attacker sends this type of packets to the TCP port139 (NetBIOS) of the host with the Operation System bugs, which will cause the host with a blue screen. Ping of Death attack means that the attacker sends abnormal ping packets larger than 65535 bytes to cause system crash on the target computer. Smurf attack is a distributed denial-of-service attack in which large numbers of Internet Control Message Protocol (ICMP) packets with the intended victim's spoofed source IP are broadcast to a computer network using an IP broadcast address. Most devices on a network will, by default, respond to this by sending a reply to the source IP address. If the number of machines on the network that receive and respond to these packets is very large, the victim's computer will be flooded with traffic. 2.2 Using the CLI Follow these steps to configure DoS Defend: Step 1 configure Enter global configuration mode. Step 2 ip dos-prevent Globally enable the DoS defend feature. User Guide 818