Network : Network > DNS
DNA and IPv4
The IPv4 page has these sections:
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IPv4 DNS Settings
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DNS Rebinding Attack Prevention
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DNS Binding for FQDN
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DNS Cache
IPv4 DNS Settings
In the IPv4 DNS Settings section, select one of the following:
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Specify IPv4 DNS Servers Manually and enter the IP address(es) into the DNS Server fields.
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To use the DNS Settings configured for the WAN zone, select Inherit IPv4 DNS Settings Dynamically from WAN Zone and enter the IP address(es) into the DNS Server fields.
Click Accept to save your changes.
DNS Rebinding Attack Prevention
DNS rebinding is a DNS-based attack on code embedded in web pages. Normally requests from code embedded in web pages (JavaScript, Java, and Flash) are bound to the web-site they are originating from (see Same Origin Policy). A DNS rebinding attack can be used to improve the ability of JavaScript based malware to penetrate private networks, and subvert the browser's same-origin policy.
DNS rebinding attackers register a domain which is delegated to a DNS server they control. The server is configured to respond with a very short TTL parameter which prevents the result from being cached. The first response contains IP address of the server hosting the malicious code. Any subsequent requests contain IP addresses from private (RFC 1918) network, presumably behind a firewall, being target of the attacker. Because both are fully valid DNS responses, they authorize the sandbox script to access hosts in a private network. By iterating addresses in these short-term but still valid DNS replies the script is able to scan the network and perform other malicious activities.
To configure DNS rebinding attack prevention:
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Select the Enable DNS Rebinding Attack Prevention checkbox.
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From the Action drop-down menu, select an action to perform when a DNS rebinding attack is detected:
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Log Attack
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Log Attack & Return a Query Refused Reply
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Log Attack & Drop DNS Reply
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From the Allowed Domains drop-down menu, select an allowed domain FQDN Address Object or FQDN Address Object Group containing allowed domain-names (such as, *.sonicwall.com) for which locally connected/routed subnets should be considered legal responses.
You can also create new FQDN address objects or FQDN address object groups by selecting Create new FQDN Address Object… or FQDN Address Object Group….
DNS Binding for FQDN
To enable DNS binding for FQDN, select the FQDN Object Only Cache DNS Reply from Sanctioned Server checkbox.
DNS Cache
To show the contents of the general DNS cache, click the Show DNS Cache button. A pop-up window displays the following cache contents:
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What
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DNS Name
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IP Address
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TTL (secs)