Although the practice is unsanctioned by the university, and students have sometimes been arraigned on trespassing charges for hacking, hacks have substantial significance to MIT's history and student culture. Student bloggers working for the MIT Admissions Office have often written about MIT hacks, including those occurring during Campus Preview Weekend (CPW), an event welcoming admitted prospective freshman students. Alumni bloggers on the MIT Alumni Association website also report and document some of the more memorable hacks. Since the mid-1970s, the student-written guide "How To Get Around MIT (HowToGAMIT)" has included a chapter on hacking, and discusses history, hacker groups, ethics, safety tips, and risks of the activity.