Asterisk introduced a security log level in 1.8.
The reference manual is here.
At the moment this can be configured manually in /etc/asteris/logger_logfiles_custom.conf
security => security
but it would be good if this could be configured via the freepbx logfiles setting module that would require an additional combobox for Secure log level and default settings which sets up the security file with securitly log level.