ESR service routers. ESR-Series. Functionality description. Version 1.12.0
272
Command
Description
ip firewall screen spy-blocking icmp-type
time-exceeded
The given command enables the blocking of all 11 type ICMP packets
(time exceeded) including the packets generated by the router itself.
The protection prevents an attacker from learning about network
topology and hosts availability
ip firewall screen spy-blocking ip-sweep
The given command enables the protection against IP-sweep attacks.
When the protection is enabled, if more than 10 ICMP queries from one
source arrive within the specified interval, the first 10 queries are
dropped by the router and 11th with the following ones are discarded
for the remaining interval time. The protection prevents an attacker
from learning about network topology and hosts availability.
ip firewall screen spy-blocking port-scan
The given command enables the protection against port scan attacks.
If more than 10 TCP packets with the SYN flag arrive to several TCP
ports and or more than 10 UDP packets arrive ti several UDP ports of
one source within the first specified interval (<threshold>), then this
behaviour is recorded as port scan attack and all the following packets
of that type are blocked for the second specified time interval (<TIME>).
An attacker will not be able to scan the device open ports quickly.
ip firewall screen spy-blocking spoofing
The given command enables the protection against ip spoofing
attacks. When the protection is enabled, the router checks packets for
matching the source address and routing table entries, and in case of
mismatch the packet is dropped. For example, if a packet with source
address 10.0.0.1/24 arrives to the Gi1/0/1 interface and the given
subnet is located after the Gi1/0/2 interface in the routing table, it is
considered that the source address has been replaced. Protects from
network intrusions with replaced source IP addresses.
ip firewall screen spy-blocking syn-fin
The given command enables the blocking of TCP packets, with the SYN
and FIN flags set. These packets are specialized and it is possible to
determine a victim operational system by the respond.
ip firewall screen spy-blocking tcp-all-flag
This command enables the blocking of TCP packets, with all flags or
with the set of flags: FIN, PSH, URG. The protection against XMAS
attack is provided.
ip firewall screen spy-blocking tcp-no-flag
This command enables the blocking of TCP packets with the zero
'flags' field. These packets are specialized and it is possible to
determine a victim operational system by the respond.
ip firewall screen suspicious-packets icmp-
fragment
The given command enables the blocking of fragmented ICMP packets.
ICMP packets are usually small and there is no need to fragment them.
ip firewall screen suspicious-packets ip-
fragment
The given command enables the blocking of fragmented packets.
ip firewall screen suspicious-packets large-
icmp
The given command enables the blocking of ICMP packets more than
1024 bytes.