The IPS blade is not capable of sending UserChecks to the end user, and will simply start dropping packets or in some cases issue a TCP reset (whether a particular IPS protection performs a drop or reject upon a prevent action cannot be changed). So if a user gets blocked but doesn’t seem to see a UserCheck, the IPS blade may well be responsible. This was covered in my IPS/AV/ABOT Immersion course.
IPS/AV/ABOT Immersion & Max Capture: Know your Packets
Self-Guided Video Series available at www.maxpowerfirewalls.com