Dos Defend - TP-Link T2600G-28TS User Manual

13.8 DoS Defend

DoS (Denial of Service) Attack is to occupy the network bandwidth maliciously by the network
attackers or the evil programs sending a lot of service requests to the Host, which incurs an
abnormal service or even breakdown of the network.
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 several types of DoS attack
listed in the following table.
DoS Attack Type
Land Attack
Scan SYNFIN
Xmascan
NULL Scan Attack
SYN packet with its
source port less than
1024
Blat Attack
Ping Flooding
SYN/SYN-ACK
Flooding
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.
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.
The attacker sends the illegal packet with its TCP index, FIN, URG and
PSH field set to 1.
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.
The attacker sends the illegal packet with its TCP SYN field set to 1
and source port less than 1024.
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.
The attacker floods the destination system with Ping broadcast storm
packets to forbid the system to respond to the 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.
Table 13-1 Defendable DoS Attack Types
274
Description