Today I found the following in the daily logwatch of my debian server:
--------------------- Connections (secure-log) Begin ------------------------
**Unmatched Entries**
sg: user 'root' (login '???' on ???) returned to group 'root': 1 Time(s)
sg: user 'root' (login '???' on ???) switched to group 'list': 1 Time(s)
---------------------- Connections (secure-log) End -------------------------
Can anyone explain to me what happend there? Should I somehow react on that?
SSH root login is disabled and only public key login is allowed. I did not login yesterday.
Thank you in advance for any explanations.