The event will be logged in /var/log/secure.log and a mail will be sent to root (which by default goes to /dev/null which is Unix speak for it is discarded).
+1 Sending the mail shouldn't fail, but probably won't be read. It is possible to have it sent to a different user, but the chances of that modification are about the same as someone reading root's mail. – ughoavgfhwNov 2 '11 at 22:08
I had a look at the log file in the mean time, mail to root goes to /dev/null. – patrix♦Nov 2 '11 at 22:11