BIND-9X-001004 - The host running a BIND 9.X implementation must implement a set of firewall rules that restrict traffic on the DNS interface - udp


Configuring hosts that run a BIND 9.X implementation to only accept DNS traffic on a DNS interface allows a system firewall to be configured to limit the allowed incoming ports/protocols to 53/tcp and 53/udp. Sending outgoing DNS messages from a random port minimizes the risk of an attacker guessing the outgoing message port and sending forged replies.

The TCP/IP stack in DNS hosts (stub resolver, caching/resolving/recursive name server, authoritative name server, etc.) could be subjected to packet flooding attacks (such as SYNC and smurf), resulting in disruption of communication. By implementing a specific set of firewall rules that limit accepted traffic to the interface, these risk of packet flooding and other TCP/IP based attacks is reduced.


Configure the OS firewall to only allow incoming DNS traffic on ports 53/tcp and 53/udp.
Add the following rules to the host firewall rule set:

# iptables -A INPUT -i [DNS Interface] -p tcp --dport 53 -j ACCEPT
# iptables -A INPUT -i [DNS Interface] -p udp --dport 53 -j ACCEPT
# iptables -A INPUT -i [DNS Interface] -j DROP

Note: If the system is not using an IPTables firewall, the appropriate firewall rules that limit traffic to ports 53/tcp and 53/udp should be configured on the active firewall.

See Also

Item Details


References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-207536r612253_rule, STIG-ID|BIND-9X-001004, STIG-Legacy|SV-86995, STIG-Legacy|V-72371, Vuln-ID|V-207536

Plugin: Unix

Control ID: ff7b97685bec1ffdb172c13c3ad8ba7f254c076373975ee6128cde128e69fe2f