Details

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.

Solution

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

Supportive Information

The following resource is also helpful.

• https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_ASA_STIG.zip

This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Cisco.

References

• 800-53|SC-7(11)
• CAT|II
• CCI|CCI-002403
• Rule-ID|SV-239865r665881_rule
• STIG-ID|CASA-FW-000230
• Vuln-ID|V-239865

Source

• Tenable.com/audits