3.5.2.7 Ensure loopback traffic is configured - iif lo

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:

# nft add rule inet filter input iif lo accept

# nft create rule inet filter input ip saddr 127.0.0.0/8 counter drop

IF IPv6 is enabled:

Run the following command to implement the IPv6 loopback rules:

# nft add rule inet filter input ip6 saddr ::1 counter drop

See Also

https://workbench.cisecurity.org/files/2948

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7(15), CSCv7|9.4

Plugin: Unix

Control ID: f8cbcd6b18ed4472d1e290deef5346f4d6e7db717f58eb98d62767b6cfc5b54c