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 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.
Smurf Attack By pretending to be a Host, the attacker broadcasts request packets
for ICMP response in the LAN. When receiving the request packet, all
the Hosts in the LAN will respond and send the reply packets to the
actual Host, which will causes this Host to be attacked.
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.
winNuke Attack Since the Operation System with bugs can not 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.
Table 11-1 Defendable DoS Attack Types
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