Title

The Cisco ASA must be configured to filter outbound traffic on all internal interfaces. (Cat II impact)

Discussion

If outbound communications traffic is not filtered, hostile activity intended to harm other networks or packets from networks destined to unauthorized networks may not be detected and prevented. Access control policies and access control lists implemented on devices, such as firewalls, that control the flow of network traffic ensure the flow of traffic is only allowed from authorized sources to authorized destinations. Networks with different levels of trust (e.g., the Internet) must be kept separated. This requirement addresses the binding of the egress filter to the interface/zone rather than the content of the egress filter.

Check Content

Step 1: Verify that an ingress ACL has been applied to the internal interface as shown in the example below. interface GigabitEthernet0/3 nameif INSIDE security-level 100 ip address 10.1.11.1 255.255.255.0 … … … access-group INSIDE_2_OUT in interface INSIDE Step 2: Verify that the ACL only allows outbound traffic using authorized ports and services as shown in the example below. access-list INSIDE_2_OUT extended permit tcp any any eq www access-list INSIDE_2_OUT extended permit tcp any any eq https access-list INSIDE_2_OUT extended permit tcp any any eq domain access-list INSIDE_2_OUT extended permit tcp any any eq ftp access-list INSIDE_2_OUT extended permit tcp any any eq ftp-data access-list INSIDE_2_OUT extended permit tcp any host 10.1.22.3 eq ssh access-list INSIDE_2_OUT extended deny ip any any log If the ASA is not configured to filter outbound traffic on all internal interfaces, this is a finding.

Fix Text

Step 1: Configure the egress ACL similar to the example below. ASA(config)# access-list INSIDE_2_OUT extended permit tcp any any eq https ASA(config)# access-list INSIDE_2_OUT extended permit tcp any any eq http ASA(config)# access-list INSIDE_2_OUT extended permit tcp any any eq domain ASA(config)# access-list INSIDE_2_OUT extended permit tcp any any eq ftp ASA(config)# access-list INSIDE_2_OUT extended permit tcp any any eq ftp-data ASA(config)# access-list INSIDE_2_OUT extended permit tcp any host 10.1.22.3 eq ssh ASA(config)# access-list INSIDE_2_OUT extended deny ip any any log Step 2: Apply the ACL inbound on the internal interfaces as shown in the example below. ASA(config)# access-group INSIDE_2_OUT in interface INSIDE ASA(config)# end

Additional Identifiers

Rule ID: SV-239866r855808_rule

Vulnerability ID: V-239866

Group Title: SRG-NET-000364-FW-000032

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.