Dropbolt with Through Bolts and Without -- If not, a forced entry can cause the lock to separate from the door. The typical dropbolt and rim lock should not be considered as secure as a deadbolt ...
Any exterior door that only has a lock in the door-knob isnt secure. A sturdy screwdriver or small pry bar can quickly bow the doorjamb enough to release the latch.
Are you still relying on the lock that was on the front door when you moved into your house? ... To be truly secure, any exterior door needs a deadbolt.