With DoS Defend function enabled, the switch can analyze the specific fields of the IP packets and
distinguish the malicious DoS attack packets. Upon detecting the packets, the switch will discard
the illegal packets directly and limit the transmission rate of the legal packets if the over legal
packets may incur a breakdown of the network. The switch can defend a few types of DoS attack
listed in the following table.
DoS Attack Type
Description
Land Attack
The attacker sends a specific fake SYN packet to the destination Host.
Since both the source IP address and the destination IP address of the SYN
packet are set to be the IP address of the Host, the Host will be trapped in
an endless circle for building the initial connection. The performance of the
network will be reduced extremely.
Scan SYNFIN
The attacker sends the packet with its SYN field and the FIN field set to 1.
The SYN field is used to request initial connection whereas the FIN field is
used to request disconnection. Therefore, the packet of this type is illegal.
The switch can defend this type of illegal packet.
Xmascan
The attacker sends the illegal packet with its TCP index, FIN, URG and
PSH field set to 1.
NULL Scan Attack
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 the control fields set to 0 are considered as the illegal
packets.
SYN packet with its source port
less than 1024
The attacker sends the illegal packet with its TCP SYN field set to 1 and
source port less than 1024.
Blat Attack
The attacker sends the illegal packet with its source port and destination
port on Layer 4 the same and its URG field set to 1. Similar to the Land
Attack, the system performance of the attacked Host is reduced since the
Host circularly attempts to build a connection with the attacker.
Ping Flooding
The attacker floods the destination system with Ping broadcast storm
packets to forbid the system to respond to the legal communication.
SYN/SYN-ACK Flooding
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.
Table 12-1 Defendable DoS Attack Types
On this page, you can enable the DoS Defend type appropriate to your need.
Choose the menu
Network Security
→
DoS Defend
→
DoS Defend
to load the following page.
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