3.5.3.2.3 Ensure outbound and established connections are configured

Information

Configure the firewall rules for new outbound, and established connections.

Rationale:

If rules are not in place for new outbound, and established connections all packets will be dropped by the default policy preventing network usage.

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

Solution

Configure iptables in accordance with site policy. The following commands will implement a policy to allow all outbound connections and all established connections:

# iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A OUTPUT -p udp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A OUTPUT -p icmp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A INPUT -p tcp -m state --state ESTABLISHED -j ACCEPT
# iptables -A INPUT -p udp -m state --state ESTABLISHED -j ACCEPT
# iptables -A INPUT -p icmp -m state --state ESTABLISHED -j ACCEPT

See Also

https://workbench.cisecurity.org/files/2925

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

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

Plugin: Unix

Control ID: ad1fa5bfcd968a9b5d19f1fd79dcaf1cd1b1af733e4c03a027a71b498aa6a04b