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The Cisco ASA perimeter firewall must be configured to block all outbound management traffic.


Overview

Finding ID Version Rule ID IA Controls Severity
V-239867 CASA-FW-000250 SV-239867r891331_rule Medium
Description
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.
STIG Date
Cisco ASA Firewall Security Technical Implementation Guide 2024-06-06

Details

Check Text ( C-43100r891329_chk )
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 (F-43059r891330_fix)
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