When I was in college, we had the report of a peeping Tom and we were all warned to stay inside with the doors locked (back in the days when there was no security on any buildings). We all poo-poo’d it but did walk with friends at night and took a few more precautions. The Peeping Tom? Ted Bundy. He moved on to Florida and did break in and kill two women in the off campus apartment.
And really, if frat boys could break into sorority houses without much trouble, anyone can get past the security of three 18 year olds playing cards at the front desk of a dorm. And the danger might not be from someone from the outside but from another student living in your dorm.