Security Considerations

• Disallow routes to countries that customers don't need, especially high fraud countries.
• Set a daily spending limit and maximum concurrent calls limit for all customers.
• Requiring long password lengths for phones and people.
• Educate customers on choosing good passwords.
• Have contracts to make sure the right person pays if they are hacked and run up a huge bill.
• Change the SSH port from 22 to something non standard.
• Use iptables to lock out countries where you do not have customers.
• Set Asterisk servers to use non default ports for SIP like 5065 instead of 5060.
• Make sure all handsets have a username and password which are not the devices default.
• Monitor servers with a tool like Nagios and or Cacti where there is an alert if there is more than X calls per customer, system etc.

Some systems have easySysAdmin or fail2ban (for example) automatically block brute force SSH or SIP registration attacks.