ZyXEL Communications P-334WT Support Notes page 23

series of IP fragments with overlapping offset fields. When these fragments are reassembled at the
destination, some systems will crash, hang, or reboot.
9. What is SYN Flood attack?
SYN attack floods a targeted system with a series of SYN packets. Each packet causes the targeted
system to issue a SYN-ACK response, While the targeted system waits for the ACK that follows the
SYN-ACK, it queues up all outstanding SYN-ACK responses on what is known as a backlog queue.
SYN-ACKs are moved off the queue only when an ACK comes back or when an internal timer
(which is set a relatively long intervals) terminates the TCP three-way handshake. Once the queue is
full , the system will ignore all incoming SYN requests, making the system unavailable for
legitimate users.
10. What is LAND attack?
In a LAN attack, hackers flood SYN packets to the network with a spoofed source IP address of the
targeted system. This makes it appear as if the host computer sent the packets to itself, making the
system unavailable while the target system tries to respond to itself.
11 What is Brute-force attack?
A Brute-force attack, such as 'Smurf' attack, targets a feature in the IP specification known as
directed or subnet broadcasting, to quickly flood the target network with useless data. A Smurf
hacker flood a destination IP address of each packet is the broadcast address of the network, the
router will broadcast the ICMP echo request packet to all hosts on the network. If there are
numerous hosts, this will create a large amount of ICMP echo request packet, the resulting ICMP
traffic will not only clog up the 'intermediary' network, but will also congest the network of the
spoofed source IP address, known as the 'victim' network. This flood of broadcast traffic consumes
all available bandwidth, making communications impossible.
12. What is IP Spoofing attack?
Many DoS attacks also use IP Spoofing as part of their attack. IP Spoofing may be used to break into
systems, to hide the hacker's identity, or to magnify the effect of the DoS attack. IP Spoofing is a
technique used to gain unauthorized access to computers by tricking a router or firewall into
thinking that the communications are coming from within the trusted network. To engage in IP
Spoofing, a hacker must modify the packet headers so that it appears that the packets originate from
a trusted host and should be allowed through the router or firewall.
13. Why traffic redirect/static/policy route be blocked by P-334WT?
P-334WT is a secure gateway for all data passing between the Internet and the LAN. For
some reasons (load balance or backup line), users may want traffic to be re-routed to another
Internet access devices while still be protected by Prestige. In such case, the network topology
is the most important issue. Here is a common example that people mis-deploy the LAN
traffic redirect and static route.