3.6.2.2 Ensure IPv4 loopback traffic is configured - OUTPUT

Information

Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network (127.0.0.0/8).

Rationale:

Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network (127.0.0.0/8) traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.

Note: Changing firewall settings while connected over network can result in being locked out of the system.

Solution

Run the following commands to implement the loopback rules:

# iptables -A INPUT -i lo -j ACCEPT
# iptables -A OUTPUT -o lo -j ACCEPT
# iptables -A INPUT -s 127.0.0.0/8 -j DROP

See Also

https://workbench.cisecurity.org/files/3144

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7(12), CSCv7|9.4

Plugin: Unix

Control ID: ab4905dbf11415ddfbb41547039575bcc53b31c8b509880189534351d3e27dd8