Title

The Cisco ASA perimeter firewall must be configured to block all outbound management traffic. (Cat II impact)

Discussion

The management network must still have its own subnet in order to enforce control and access boundaries provided by Layer 3 network nodes such as routers and firewalls. Management traffic between the managed network elements and the management network is routed via the same links and nodes as that used for production or operational traffic. Safeguards must be implemented to ensure that the management traffic does not leak past the managed network's premise equipment. If a firewall is located behind the premise router, all management traffic must be blocked at that point, with the exception of management traffic destined to premise equipment.

Check Content

Review the ASA configuration to determine if it blocks outbound management traffic. Step 1: Verify that an ingress ACL has been applied to all internal interfaces as shown in the example below. interface GigabitEthernet0/0 nameif INSIDE security-level 100 ip address x.1.11.1 255.255.255.0 … … … access-group INSIDE_IN in interface INSIDE Step 2: Verify that the ingress ACL blocks outbound management traffic as shown in the example below. access-list INSIDE_IN extended deny udp any any eq snmp access-list INSIDE_IN extended deny udp any any eq snmptrap access-list INSIDE_IN extended deny udp any any eq ntp access-list INSIDE_IN extended deny udp any any eq syslog access-list INSIDE_IN extended deny tcp any any eq 22 access-list INSIDE_IN extended deny tcp any any eq tacacs access-list INSIDE_IN extended permit ip any any Note: An exception is to allow management traffic destined to perimeter devices. In those cases, configure permit statements for that traffic before the deny statements in the example above. If the ASA is not configured to block outbound management traffic, this is a finding.

Fix Text

Step 1: Configure the ingress ACL similar to the example below. ASA(config)# access-list INSIDE_IN extended deny udp any any eq snmp ASA(config)# access-list INSIDE_IN extended deny udp any any eq snmptrap ASA(config)# access-list INSIDE_IN extended deny udp any any eq ntp ASA(config)# access-list INSIDE_IN extended deny udp any any eq syslog ASA(config)# access-list INSIDE_IN extended deny tcp any any eq 22 ASA(config)# access-list INSIDE_IN extended deny tcp any any eq tacacs ASA(config)# access-list INSIDE_IN extended permit ip any any Step 2: Apply the ACL inbound on the internal interfaces as shown in the example below. ASA(config)# access-group INSIDE_IN out interface INSIDE ASA(config)# end

Additional Identifiers

Rule ID: SV-239867r891331_rule

Vulnerability ID: V-239867

Group Title: SRG-NET-000364-FW-000035

Expert Comments

CCIs tied to check.

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