Hey there.
I found an old post here
What the %$#@ is pam_unix (cron:session) doing every ten minutes? (/var/log/auth.log)
and I have same problem..
Know it's normal, but size of the log directory is bigger every day by more than 50 MB. So that's a problem. Can I do something with this?
Also I found this thread -
removing cron entries from auth.log, but when I opened my cron.hourly/ directory, it seems to be empty...
I'm using ispCP hosting software on my server .. It could be related somehow
Thanks for an advices!