Hi .. yes indeed the ASA also supports those basics IDS features .. but they are basic and statics. if you want to be serious about packet inspections then you really need to opt for a IPS module or a sensor.
I hope it helps .. please rate it if it does !!
From Cisco Doc:
"Step 1 To define an IP audit policy for informational signatures, enter the following command:
hostname(config)# ip audit name name info [action [alarm] [drop] [reset]]
Where alarm generates a system message showing that a packet matched a signature, drop drops the
packet, and reset drops the packet and closes the connection. If you do not define an action, then the
default action is to generate an alarm.
Step 2 To define an IP audit policy for attack signatures, enter the following command:
hostname(config)# ip audit name name attack [action [alarm] [drop] [reset]]
Where alarm generates a system message showing that a packet matched a signature, drop drops the
packet, and reset drops the packet and closes the connection. If you do not define an action, then the
default action is to generate an alarm.
Step 3 To assign the policy to an interface, enter the following command:
ip audit interface interface_name policy_name
Step 4 To disable signatures, or for more information about signatures, see the ip audit signature command in
the Cisco Security Appliance Command Reference."
