3.5.2.9 Ensure default deny firewall policy - forward

Information

A default deny all policy on connections ensures that any unconfigured network usage will be rejected.

Rationale:

With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to white list acceptable usage than to black list unacceptable usage.

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

Solution

Run the following command for the base chains with the input, forward, and output hooks to implement a default DROP policy:

# nft chain <table family> <table name> <chain name> { policy drop ; }

Example:

# nft chain inet filter input { policy drop ; }

# nft chain inet filter forward { policy drop ; }

# nft chain inet filter output { policy 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: 2478907e7e2fd14e5d824a0ab5daeffe99fb75db854a9e3e8a71f0e0e777f748