A password was used to gain access to restricted resources.
Madrigal LaFayette used "JOHANN” as her simularity password. (PROSE: Lucifer Rising)
The Ninth Doctor told Mickey Smith to use the password "buffalo" to access a variety of areas of the UNIT website. (TV: World War Three)
Hr'oln was Eve's first pet and also her password to the Museum of the Last Ones. (PROSE: The Last Dodo)
"Crimson Eleven Delight Petrichor" was the telepathic password to access one of the back-up TARDIS control rooms. (TV: The Doctor's Wife)
"rycbar123" was the password used to access the Maitland family Wi-Fi. (TV: The Bells of Saint John)