Hi,
I think using the Threat Detection on the ASA device would also be a possible option for you.
NOTE:- Still after enabling the threat detection , you might need to modify some of the setting on the ASA device for the same.
http://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/113685-asa-threat-detection.html
Thanks and Regards,
Vibhor Amrodia