Draytek 2900 - Manual (Page 89)

Vigor2900 Series User’s Guide 83
header. The reason for limitation is IP option appears to be a
vulnerability of the security for the LAN because it will carry
significant information, such as security, TCC (closed user group)
parameters, a series of Internet addresses, routing messages...etc. An
eavesdropper outside might learn the details of your private
networks.
Block Land Check the box to enforce the Vigor router to defense the Land
attacks. The Land attack combines the SYN attack technology with
IP spoofing. A Land attack occurs when an attacker sends spoofed
SYN packets with the identical source and destination addresses, as
well as the port number to victims.
Block Smurf Check the box to activate the Block Smurf function. The Vigor router
will ignore any broadcasting ICMP echo request.
Block trace router Check the box to enforce the Vigor router not to forward any trace
route packets.
Block SYN fragment Check the box to activate the Block SYN fragment function. The
Vigor router will drop any packets having SYN flag and more
fragment bit set.
Block Fraggle Attack Check the box to activate the Block fraggle Attack function. Any
broadcast UDP packets received from the Internet is blocked.
Activating the DoS/DDoS defense functionality might block some
legal packets. For example, when you activate the fraggle attack
defense, all broadcast UDP packets coming from the Internet are
blocked. Therefore, the RIP packets from the Internet might be
dropped.
Block TCP flag scan Check the box to activate the Block TCP flag scan function. Any TCP
packet with anomaly flag setting is dropped. Those scanning activities
include no flag scan, FIN without ACK scan, SYN FINscan, Xmas
scan and full Xmas scan.
Block Tear Drop Check the box to activate the Block Tear Drop function. Many
machines may crash when receiving ICMP datagrams (packets) that
exceed the maximum length. To avoid this type of attack, the Vigor
router is designed to be capable of discarding any fragmented ICMP
packets with a length greater than 1024 octets.
Block Ping of Death Check the box to activate the Block Ping of Death function. This
attack involves the perpetrator sending overlapping packets to the
target hosts so that those target hosts will hang once they
re-construct the packets. The Vigor routers will block any packets
realizing this attacking activity.
Block ICMP Fragment Check the box to activate the Block ICMP fragment function. Any
ICMP packets with more fragment bit set are dropped.
Block Land Check the box to enforce the Vigor router to defense the Land
attacks. The Land attack combines the SYN attack technology with
IP spoofing. A Land attack occurs when an attacker sends spoofed
SYN packets with the identical source and destination addresses, as
well as the port number to victims.
Block Unknown
Protocol Check the box to activate the Block Unknown Protocol function.
Individual IP packet has a protocol field in the datagram header to
indicate the protocol type running over the upper layer. However,