Dunno what made me think of this just now. When I worked for IT in a school district way back in the 90s, a librarian told me she kept a supply of mouse balls in her desk because kids would steal them out of the school computers. What I remember about those balls was they picked up dust and crud off surfaces. Pretty soon optical mice came along and they were history.
For us it was putting a space in the username field of the login screen, and then moving the cursor back to the start of the field.
The username field wouldn’t reset on a failed login attempt, only the password field did. So users would do a visual scan of the username field, confirm that’s correct, assume they miskeyed when entering their password, try again, rinse and repeat.
That and rotating the desktop, switching the keyboard to Dvorak, etc