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ServerIron ADX Security Guide 45
53-1002440-03
DNS attack protection
1
Once a packet matches a configured filter, the following actions can be specified:
• drop
• Redirect to a server or server group
• rate-limit
• log (log is a secondary action and cannot be specified by itself)
The actions are configured within the DNS DPI policy as shown in the following.
ServerIron(config)# csw-policy DNSpolicy1 type dns-filter
ServerIron(config-csw-dns-policy-P1) match rule1 redirect 1 log
ServerIron(config-csw-dns-policy-P1) match rule2 drop log
ServerIron(config-csw-dns-policy-P1) match rule3 rate-limit monitor-interval 2
conn-rate 20 hold-down-time 2 log
ServerIron(config-csw-dns-policy-P1) default drop
Syntax: { match <rule-name> | default } {drop | redirect <group>| rate-limit monitor-interval
<mon-value> conn-rate <conn-value> hold-down-time <hold-down-value> } { log | no-log }
If the default option is configured under a policy, DNS query packets that do not match any of the
rules bound to that policy are acted on by the configured policy. In the example above, a DNS query
that does not match rules rule1, rule2, and rule3 will be dropped.
The drop parameter directs the ServerIron ADX to drop any packets that match the filter.
The redirect parameter directs the ServerIron ADX redirect any packets that match the filter to a
server or server group specified by <server-id> or <server-grp-id>
The rate-limit parameter directs the ServerIron ADX to rate limit packets that match the filter at the
monitor-interval specified by the <mon-value> variable, the conn-rate specified by the
<conn-value> and the hold-down-time specified by the <hold-down-value> variable.
The log parameter directs the ServerIron ADX to report the number of times that a rule has been
matched within a 5 second interval. log is a secondary action and cannot be specified by itself.
Binding a DNS DPI policy to a Virtual port
To take effect, a DNS DPI policy must be bound to a virtual port. The following applies to this
binding:
• a CSW DNS policy can only be applied to port DNS
• You can bind only one policy per virtual port
• You cannot bind a DNS policy to a virtual port if another CSW policy is already bound to port
DNS.
• Once a DNS policy is bound to a port, any DNS query that comes to the virtual server will be
matched against the rules bound to that policy and any associated action will be take on the
match.
You can bind a DNS DPI policy to a virtual port as shown.
ServerIron(config) server virtual vip1 10.120.62.53
ServerIron(config-vs-vip1)# port dns csw-policy DNSpolicy1
ServerIron(config-vs-vip1)# port dns csw
Syntax: [no] port dns csw-policy <policy-name>
The <policy-name> variable specifies the name of the policy to be bound to a virtual port.
Syntax: [no] port dns csw