IPS actions allow you to execute custom responses to events.
Unlike loggers, these are invoked before thresholding and can be used to
control external agents (including loggers).

IPS rules have an associated type that determines what kind of action they
trigger. The rule types defined in this module are:

* log
* pass
* alert
* drop
* block
* reset

There is also a "none" rule type, which is a no-op.

It also defines 3 active responses:
* react
* reject
* rewrite

Reject performs active response to shutdown hostile network 
session by injecting TCP resets (TCP connections) or ICMP unreachable 
packets.

React sends an HTML page to the client, a RST to the server
and blocks the flow. It is using payload_injector utilty.
payload_injector should be configured when react is used.

Rewrite enables overwrite packet contents based on "replace" 
option in the rules.
