Sexual harassment is illegal. You will find lots of helpful information on this website, and you may also want to take a look at Stanford's policy that specifically prohibits sexual harassment.
You may be concerned about retaliation if you talk to someone‑-particularly if the person causing the harassment is a supervisor, a teacher, or someone else who has power over you. Under no circumstances will Stanford allow reprisals against a person who in good faith reports or provides information about sexual harassment or behavior that might constitute sexual harassment.
On the other hand, intentionally making a false report or providing false information is grounds for discipline.
Report it! Sexual harassment is not tolerated at Stanford University. We are here to help. Report matters to Stanford's Title IX Coordinator at firstname.lastname@example.org.
Consult. If you're not ready to report, consult with one of Stanford's resources for further help and guidance. These people can provide support and advice about Stanford's policy and procedures, and can help you explore options towards resolution.
Ask for the conduct to stop. We are here to assist you but if you would like to manage this on your own, it is okay to clearly and firmly state directly to the harasser that you want a particular behavior to cease. This is not a time to be polite or vague.