Possible to change cron link?

I use D6. Cron run often by some bots visiting example.com/cron.php Is it possible to change it somehow? Or restrict? I would like to prevent anonymous users to hit the script.I want to be able to run cron from drupal admin interface and also to run it automatically from linux crontab. I tried to set permissions to read for owner only (www-data is group) but it does not help.

Thank you.