Title

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

Discussion

Unrestricted traffic to the trusted networks may contain malicious traffic that poses a threat to an enclave or to other connected networks. Additionally, unrestricted traffic may transit a network, which uses bandwidth and other resources. Firewall filters 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.

Check Content

Review the ASA configuration to verify that it is filtering inbound traffic on all external interfaces. access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.2 eq www access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.2 eq https access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.3 eq ftp access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.3 eq ftp-data access-list OUTSIDE_2_DMZ extended deny ip any any log … … … access-group OUTSIDE_2_DMZ in interface OUTSIDE If the ASA is not configured to filter inbound traffic on all external interfaces, this is a finding.

Fix Text

Step 1: Configure the ACL to allow specific inbound traffic. ASA(config)# access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.2 eq www ASA(config)# access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.2 eq https ASA(config)# access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.3 eq ftp ASA(config)# access-list OUTSIDE_2_DMZ extended permit tcp any host 10.1.33.3 eq ftp-data ASA(config)# access-list OUTSIDE_2_DMZ extended deny ip any any log Step 2: Apply the ACL inbound to the external interface. ASA(config)# access-group OUTSIDE_2_DMZ in interface OUTSIDE

Additional Identifiers

Rule ID: SV-239865r855807_rule

Vulnerability ID: V-239865

Group Title: SRG-NET-000364-FW-000031

Expert Comments

CCIs tied to check.

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