cyberstrikeus 3.6.4 Ensure outbound and established connections are configured (Not Scored)
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Description
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.
Audit Procedure
Run the following command and verify all rules for new outbound, and established connections match site policy:
iptables -L -v -n
Expected Result
Rules should exist that allow new outbound connections and established inbound connections according to site policy.
Remediation
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
Default Value
Not configured. Note: 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.
References
- CIS Controls: 9.2 - Leverage Host-based Firewalls
Profile
- Level 1 - Server
- Level 1 - Workstation