vlock - 2.2.2-12+b1 main

vlock either locks the current terminal (which may be any kind of terminal,
local or remote), or locks the entire virtual console system, completely
disabling all console access. vlock gives up these locks when either the
password of the user who started vlock or the root password is typed.
.
vlock is interesting on multi user system environments. vlock allows users
to lock their sessions while other users can still use the same system via
other virtual terminal.
.
vlock is very useful for users security.