Security check

We just switched to Asterisk, the old system we had (freeswitch) built by security expert so we trusted him to check all that.
Right now I feel less safe when I know I’m running stock installation without any security enhancements/checks.

What do you think is the best thing to do right now? There’s a website/manual/book you can recommend on this subject? Do you thing the stock configurations are good enough? any tools/tips to check stuff?

thanks in advance.


Here’s a good primer: