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/2948

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-7b., CSCv7|9.4

Plugin: Unix

Control ID: e808a6d5ccfc7042f3d76f8ffb690f2621d551430fbcfa0855c3cfe7fe7debb5