Hi.

You might try:

Linux System Security
ISBN: 0-13-015807-0
Authors: Scott Mann & Ellen L. Mitchell

The Tiger security program is covered pretty well. On page 362, they explain the check_cron script along with several others. In fact, pages 341 - 379 are all about Tiger ( where to obtain it, installation, configuration, etc. ). The book is quite good as it covers many security tools in detail.

Hope this helps,
-DK