The Cisco CSC-SSM-20 modules provide advanced scanning technologies within the Cisco ASA firewall. During installations of these modules I created some quick notes, which I would like to share with you.
After inserting the Cisco CSC-SSM modules into the Cisco ASA firewall, you have two ways to configure the initial configuration. The first method is through Cisco ASDM and launching the Cisco CSC-SSM Launch Wizard under Configuration. The second method is through the Cisco ASA CLI. Below you see an example of the CLI method.
session 1 do setup ac-key base 1 <license key>
session 1 do setup ac-key plus 1 <license key>
session 1 ip address 10.10.1.1 255.255.255.0
session 1 ip gateway 10.10.1.1
session 1 do setup dns 10.10.1.10 10.10.1.11
session 1 do setup host csc-ssm1.booches.nl
session 1 do setup email-domain booches.nl
session 1 do setup ntfn-email firstname.lastname@example.org
session 1 do setup ntfn-svr-ip 10.10.1.100
session 1 do setup ntfn-svr-port 25
session 1 do setup password <old password> <new password>
session 1 do apply-config
The above commands configure various parameters, like license keys, hostname, IP address, internal mail domain and password credentials.
Define scanning traffic
With the configuration of a service-policy within the Cisco ASA configuration, you define which traffic should be forwarded and scanned by the CSC-SSM modules. The Cisco CSC-SSM modules provide scanning for the following protocols: tcp/http, tcp/smtp, tcp/pop3 and tcp/ftp. The Cisco CSC-SSM modules have their own management interface. This interface is used by the Cisco CSC-SSM modules to check for updates or query the TrendMicro databases for web or e-mail reputation checks. I always exempt the traffic from the Cisco CSC-SSM modules from scanning, because scanning the Cisco CSC-SSM traffic could impact the performance. Below you see and example configuration of the service-policy configuration, including the exemption of the Cisco SSM traffic. The Cisco SSM modules have the IP addresses 10.10.1.1 and 10.10.1.2 in this example.
access-list csc-ssm extended deny tcp host 10.10.1.1 any eq www
access-list csc-ssm extended deny tcp host 10.10.1.1 any eq smtp
access-list csc-ssm extended deny tcp host 10.10.1.1 any eq pop3
access-list csc-ssm extended deny tcp host 10.10.1.1 any eq ftp
access-list csc-ssm extended deny tcp host 10.10.1.2 any eq ftp
access-list csc-ssm extended deny tcp host 10.10.1.2 any eq pop3
access-list csc-ssm extended deny tcp host 10.10.1.2 any eq smtp
access-list csc-ssm extended deny tcp host 10.10.1.2 any eq www
access-list csc-ssm extended permit tcp any any eq www
access-list csc-ssm extended permit tcp any any eq smtp
access-list csc-ssm extended permit tcp any any eq pop3
access-list csc-ssm extended permit tcp any any eq ftp
match access-list csc-ssm
service-policy pm-csc-scanning interface inside
The policy-map uses csc fail-open, which means that all traffic is allowed through if the Cisco CSC-SSM module would (physically) fail and become unavailable. Depending on the security policy used within your organization, you can also configure the Cisco ASA to block all traffic. You should then use the command csc fail-closed.
I configured the service-policy on the inside interface. This is done for logging purposes. When you apply the service-policy to the outside interface, you will only see the outside PAT address in the http logging. Which is fairly useless if you would like to know who is accessing an “illegal” website.
Before placing the Cisco CSC-SSM module in production, be sure that the Cisco CSC-SSM module has access to the internet to query the TrendMicro database. If the Cisco CSC-SSM modules don’t have the appropriate rights to the internet the scanning feature doesn’t work properly and nobody will have access to the internet.
Failover / Synchronization
Cisco ASA appliances are mostly configured in a redundant way, like active/passive or active/active. When both Cisco ASA appliances have their own Cisco CSC-SSM module, you can configure synchronization between the Cisco CSC-SSM modules. This ensures that the configuration of both modules is always the same. I configure failover / synchronization with the following steps.
Be sure you do not click Synchronize to peer at the end of step 7, while you are still on the Device Failover Settings window for the secondary device. If you do, the configuration you have already set up on the primary device is erased. You must perform manual synchronization from the primary device, as described in step 8. The exception to the auto-synchronization feature is uploading a system patch. A patch must be applied on both the primary and the secondary device.