3.6.3.2.2 Ensure 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).

Notes:

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

Remediation will only affect the active system firewall, be sure to configure the default policy in your firewall management to apply on boot as well

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.

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/2920

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

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

Plugin: Unix

Control ID: 55a051dd194816d79feed4b26ea67f224394002f2f1a6757d37f68e8cf292dee