Sudoers File Error – Meaning of ‘X is not in the sudoers file. This incident will be reported.’

sudouser interface

Along side the question "Username is not in the sudoers file. This incident will be reported" that explained the programical aspects of the error and suggested some workarounds, I want to know: what does this error mean? 

X is not in the sudoers file.  This incident will be reported.

The former part of the error explains, clearly, the error. But the second part says that "This error will be reported"?! But why? Why the error will be reported and where? To whom? I'm both user and administrator and didn't receive any report :)!

Best Answer

The administrator(s) of a system are likely to want to know when a non-privileged user tries but fails to execute commands using sudo. If this happens, it could be a sign of

  1. a curious legitimate user just trying things out, or
  2. a hacker trying to do "bad things".

Since sudo by itself can not distinguish between these, failed attempts to use sudo are brought to the attention of the admins.

Depending on how sudo is configured on your system, any attempt (successful or not) to use sudo will be logged. Successful attempts are logged for audit purposes (to be able to keep track of who did what when), and failed attempts for security.

On a fairly vanilla Ubuntu setup that I have, this is logged in /var/log/auth.log.

If a user gives the wrong password three times, or if they are not in the sudoers file, an email is sent to root (depending on the configuration of sudo, see below). This is what's meant by "this incident will be reported".

The email will have a prominent subject:

Subject: *** SECURITY information for thehostname ***

The body of the message contains the relevant lines from the logfile, for example

thehostname : Jun 22 07:07:44 : nobody : user NOT in sudoers ; TTY=console ; PWD=/some/path ; USER=root ; COMMAND=/bin/ls

(Here, the user nobody tried to run ls through sudo as root, but failed since they were not in the sudoers file).

No email is sent if (local) mail has not been set up on the system.

All of these things are configurable as well, and that local variations in the default configuration may differ between Unix variants.

Have a look at the mail_no_user setting (and related mail_* settings) in the sudoers manual (my emphasis below):

mail_no_user

If set, mail will be sent to the mailto user if the invoking user is not in the sudoers file. This flag is on by default.

Related Question