Security: Secrets and Hype

Good VoIP Deployment Guidelines (Do Not Exist?)

Knowledge on security issues is a two-edged sword. Knowing enough of security will empower you to make right choices. But knowing too much can make you paranoid. So what, if all VoIP systems can be broken into? Or can they? Or do you really want to know?

Some people argue that you should not care about VoIP issues unless they impact your own VoIP deployment. With this thinking, why would I care about Microsoft problems as a Mac user? The answer is simple: I am in the security business, so I should know about security issues in any platform. If you are in VoIP security business, your job is much easier as you only need to know about VoIP security issues in any architecture and platform. Knowledge about vulnerabilities in one specific domain will help you analyze similar flaws in another domain. No tool can do that for you. It is not only about knowledge of issues, but how you use that knowledge to find new issues.

Building a VoIP architecture does not start from security mechanisms, but user requirements and budget. Although people keep saying that security is not an add-on, it really often is. But it needs to be added at the right time. Not all VoIP architectures need any security (mechanisms). The right choice of products, protocols and network architectures can take you a long way before any VoIP security solutions need to be added (if ever).

So back to the original question(s): How do I build a cheap (free) but still secure (enough) VoIP deployment?

The most common method of deploying VoIP in an Enterprise environment is using softclients, VoIP terminals running on a PC. The VoIP server can be running any open source VoIP gateway such as Asterisk or SER. The cost? Zero. Sounds attractive?

The security threats in such a simple VoIP deployment are really quite easy to enumerate:

• VoIP client has a vulnerability(Probability 100%)
• VoIP server has a vulnerability(Probability 100%)
• The PC has a vulnerability(Probability 100%)

What? That is not a threat enumeration! You are right... Let's try it the other way around:

• VoIP client has a vulnerability, with an exploit in the wild(Probability 100%)
• VoIP server has a vulnerability, with an exploit in the wild(Probability 100%)
• The PC has a vulnerability, with an exploit in the wild(Probability 100%)

We are not getting anywhere with this, are we... ;) One final time:

• VoIP client has a vulnerability, which will be exploited by someone(Probability ?%)
• VoIP server has a vulnerability, which will be exploited by someone(Probability ??%)
• The PC has a vulnerability, which will be exploited by someone(Probability ???%)

There are quite many influencing aspects in this...

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