The main drug used by students is marijuana. There are segments of people who do it, but people who end up not doing it at all. There really is not much pressure to drink or smoke. People will not force you to do it, as most people seem to mind their own business. Alcohol on campus is pretty visible. A person can easily get alcohol with a fake ID and can sneak it in passed security with relative ease. There is some drinking in dorms, and there is of course drinking at parties, too. In order to drink in campus housing, all residents must be over 21. All guests and students who are not of the legal drinking age are not allowed to be in the room. This rule, however, does not stop underage students from drinking.
The security at Iona is not overbearingly strict. If students ever get caught, it is usually because they made too much noise in their dorms and the RA ended up checking the room. One offense usually does not get you in too much trouble. If you get in trouble, you get written up and have to have a meeting with Residential Life. If you end up causing more trouble next time, you will have a very good chance of either getting banned from the residence halls or kicked out of Iona.