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3.4.3.2.2 Ensure iptables loopback traffic is configured

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

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/benchmarks/13007

Item Details

Category: SECURITY ASSESSMENT AND AUTHORIZATION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|CA-9, 800-53|SC-7, 800-53|SC-7(5), CSCv7|9.4

Plugin: Unix

Control ID: c71a546d3281c8a268dfd9036b0b85320ad942075f13c34cd89a96ce2dc596ec