The sudo timer
By default, the sudo timer is set for 5 minutes. This means that once a user performs one sudo command and enters a password, he or she can perform another sudo command within 5 minutes without having to enter the password again. Although this is obviously handy, it can also be problematic if users were to walk away from their desks with a command terminal still open. If the 5 minute timer hasn't yet expired, someone else could come along and perform some root-level task. If your security needs require it, you can easily disable this timer by adding a line to the Defaults section of the sudoers file. This way, users will have to enter their passwords every time they run a sudo command. You can make this a global setting for all users, or you can just set it for certain inpidual users.