Tigercron is used to run periodically checks from the Tiger UNIX Security Checker. Tigercron reads a control file which is usually located in '/etc/tiger/cronrc' although it can also be specificied as the first argument when calling the program. The format of this control file is the same as for the cron program, each line indicates when different checks from Tiger will be run. The user can indicate where Tiger is installed through the -B basedir parameter, any other additional options provided in the command line will be passed on to configure to configure Tiger based on them (as described in tiger (8)).
Tigercron runs the specified checks and compares their reports with previous stored reports (under /var/log/tiger). It will then mail the user defined in '/etc/tiger/tigerrc' (Tiger_Mail_RCPT) the results.
When a module is run, tigercron checks:
A differential report is generated depending on the module reports and previous run and is sent through e-mail. These reports provide an easy way to detect intrusions even if no configuration of templates has been done. In the event of an intrusion a Tiger check might detect something specific (file changes, new processes, new users, etc.) and this alert mechanism provides a way to turn Tiger into a Host Intrusion Detection System (HIDS).
The ability of it to work as a proper HIDS is based on a good customization of the cronrc file. Modules that check events to which the host is most exposed to should be run often in order to detect deviations from normal behaviour.
The deficiencies of using tigercron as a HIDS are described in the file README.hostids which is provided with the package. In Debian GNU/Linux you will find this (and other related) documentation at /usr/share/doc/tiger/