Essas entradas de log registraram uma intrusão no servidor?

Aqui estão as entradas de log que encontrei no auth.log. O que faz + ??? significar? E houve um acesso não autorizado?

Feb 11 07:48:32 tts-server su[31265]: Successful su for www-data by root
Feb 11 07:48:32 tts-server su[31265]: + ??? root:www-data
Feb 11 07:48:32 tts-server su[31265]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 11 07:48:32 tts-server su[31265]: pam_unix(su:session): session closed for user www-data
Feb 11 07:48:32 tts-server su[31275]: Successful su for www-data by root
Feb 11 07:48:32 tts-server su[31275]: + ??? root:www-data
Feb 11 07:48:32 tts-server su[31275]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 11 07:48:32 tts-server su[31275]: pam_unix(su:session): session closed for user www-data
Feb 12 09:46:27 tts-server su[11208]: Successful su for www-data by root
Feb 12 09:46:27 tts-server su[11208]: + ??? root:www-data
Feb 12 09:46:27 tts-server su[11208]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 12 09:46:27 tts-server su[11208]: pam_unix(su:session): session closed for user www-data
Feb 12 09:46:27 tts-server su[11222]: Successful su for www-data by root
Feb 12 09:46:27 tts-server su[11222]: + ??? root:www-data
Feb 12 09:46:27 tts-server su[11222]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 12 09:46:27 tts-server su[11222]: pam_unix(su:session): session closed for user www-data
Feb 13 12:25:41 tts-server su[22032]: Successful su for www-data by root
Feb 13 12:25:41 tts-server su[22032]: + ??? root:www-data
Feb 13 12:25:41 tts-server su[22032]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 13 12:25:41 tts-server su[22032]: pam_unix(su:session): session closed for user www-data
Feb 13 12:25:41 tts-server su[22043]: Successful su for www-data by root
Feb 13 12:25:41 tts-server su[22043]: + ??? root:www-data
Feb 13 12:25:41 tts-server su[22043]: pam_unix(su:session): session opened for user www-data by (uid=0)
Feb 13 12:25:41 tts-server su[22043]: pam_unix(su:session): session closed for user www-data

security log

— zuba
fonte

Provavelmente são de um trabalho cron. A partir deSecuring Debian Manual. Chapter 11 - Frequently asked Questions (FAQ)

11.2.3 Encontrei usuários fazendo 'su' nos meus logs: Estou comprometido?

Você pode encontrar linhas em seus logs como:
 Apr  1 09:25:01 server su[30315]: + ??? root-nobody
 Apr  1 09:25:01 server PAM_unix[30315]: (su) 
   session opened for user nobody by (uid=0)
Não se preocupe, verifique se isso ocorre devido a um trabalho executado no cron (geralmente /etc/cron.daily/find ou logrotate):
$ grep 25 /etc/crontab
25 6    * * *   root    test -e /usr/sbin/anacron || run-parts --report
/etc/cron.daily
$ grep nobody /etc/cron.daily/*
find:cd / && updatedb --localuser=nobody 2>/dev/null

— Rinzwind
fonte

Muito obrigado pela explicação e pelo link !! Encontrei estas linhas: ~> grep www-data /etc/cron.daily/* /etc/cron.daily/lighttpd: su -s / bin / sh -c "encontre $ cache / compress -type f -atime +30 -print0 | xargs -0 -r rm "www-data /etc/cron.daily/lighttpd: su -s / bin / sh -c" encontre $ cache / uploads -type f -atime +1 -print0 | xargs -0 -r rm "www-data

— zuba 13/02/2013