NetComm G.SHDSL 4-port Security Modem Routers NB712 - Manual (Page 51)

NB712 / NB714 User Guide 51
YML829 Rev1
Ping of Death: A ping of death attack attempts to crash your system by
sending a fragmented packet, when reconstructed is larger
than the maximum allowable size. Other known variants of
the ping of death include teardrop, bonk and nestea.
Land Attack: A land attack is an attempt to slow your network down
by sending a packet with identical source and destination
addresses originating from your network.
IP Spoofing: IP Spoofing is a method of masking the identity of an
intrusion by making it appeared that the traffic came from
a different computer. This is used by intruders to keep their
anonymity and can be used in a Denial of Service attack.
Smurf Attack: A smurf attack involves two systems. The attacker sends
a packet containing a ICMP echo request (ping) to the
network address of one system. This system is known as the
amplifier. The return address of the ping is faked (spoofed)
to appear to come from a machine on another network (the
victim). The victim is then flooded with responses to the
ping. As many responses are generated for only one attack,
the attacker is able use many amplifiers on the same victim.
Traditional firewalls are stateless meaning they have no memory of the connections of data or packets that pass
through them. Such IP filtering firewalls simply examine header information in each packet and attempt to match
it to a set of defined rule. If the firewall finds a match, the prescribed action is taken. If no match is found, the
packet is accepted into the network, or dropped, depending on the firewall configuration.
A stateful firewall maintains a memory of each connection and data passing through it. A stateful firewall records
the context of connections during each session, continuously updating state information in dynamic tables. With
this information, stateful firewalls inspect each connection traversing each interface of the firewall, testing the
validity of data packets throughout each session. As data arrives, it is checked against the state tables and if the
data is part of the session, it is accepted. Stateful firewalls enable a more intelligent, flexible and robust approach
to network security, while defeating most intrusion methods that exploit state-less IP filtering firewalls.