su to nobody

Can someone tell me what software package causes daily entrys like the below in /var/log/messages? (Suse 7.2 2.4.7-4GB) Dec 21 00:15:26 ahost su: (to nobody) root on none Dec 21 00:15:26 ahost PAM-unix2[3069]: session started for user nobody, service su Dec 21 00:18:13 ahost PAM-unix2[3069]: session finished for user nobody, service su