Draytek Vigor2912 User Manual page 219

Enable ICMP flood
defense
Enable Port Scan
detection
Block IP options
Block Land
Block Smurf
Block trace router
Block SYN fragment
Block Fraggle Attack
The default setting for threshold and timeout are 2000
packets per second and 10 seconds, respectively. That
means, when 2000 packets per second received, they will be
regarded as "attack event" and the session will be paused
for 10 seconds.
Check the box to activate the ICMP flood defense function.
Similar to the UDP flood defense function, once if the
Threshold of ICMP packets from Internet has exceeded the
defined value, the router will discard the ICMP echo
requests coming from the Internet.
The default setting for threshold and timeout are 250 packets
per second and 10 seconds, respectively. That means, when
250 packets per second received, they will be regarded as
"attack event" and the session will be paused for 10
seconds.
Port Scan attacks the Vigor router by sending lots of packets
to many ports in an attempt to find ignorant services would
respond. Check the box to activate the Port Scan detection.
Whenever detecting this malicious exploration behavior by
monitoring the port-scanning Threshold rate, the Vigor
router will send out a warning.
By default, the Vigor router sets the threshold as 2000
packets per second. That means, when 2000 packets per
second received, they will be regarded as "attack event".
Check the box to activate the Block IP options function.
The Vigor router will ignore any IP packets with IP option
field in the datagram 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.
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.
Check the box to activate the Block Smurf function. The
Vigor router will ignore any broadcasting ICMP echo
request.
Check the box to enforce the Vigor router not to forward any
trace route packets.
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.
Check the box to activate the Block fraggle Attack function.
Any broadcast UDP packets received from the Internet is
blocked.
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Vigor2912 Series User's Guide