Thanks for your interest in CMSMS PHPIDS module
The detection will start as soon as the module is installed providing
1) php version > 5.1.6 and includes SimpleXML extension(normally enabled by default)
2) you are not logged in to admin OR in the same session
The three levels allow you to toggle and set impact levels
1) If you want an email sent to you giving details of intrusion
2) If you want a warning message displayed
3) If you want to ban the intruder
All impacts will be logged in the phpids_log txt file (impact will not be logged on database if you are on local machine)
To check impact uncomment
debug_display($impact, 'impact');
on about line 437 in phpids.module.php
or for results
debug_display($result, 'results');
on about line 476 in phpids.module.php
As you mention if you enter a url like
http://YOUR SITE/?test=">XXX
this should result in an initial impact of 4 each refresh will increase this by the same amount.
For further information visit
http://php-ids.org/
Taking into account the number of reproted attacks on CMSMS sites and indeed on this forum it is worth reading Mario's white paper on 'Attack Detection'
http://docs.google.com/View?docID=dd7x5smw_11cfdd34db