Bryan Johns
Bryan Johns is the Community Director for Digium, the Asterisk company. In this role, Bryan works globally to foster growth...
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Bryan Johns | February 24, 2012 |


Security as the Enemy of Convenience in IP Communications

Security as the Enemy of Convenience in IP Communications How do you make full use of VOIP capabilities without exposing their network to the opportunity for compromise and fraud?

How do you make full use of VOIP capabilities without exposing their network to the opportunity for compromise and fraud?

VoIP technology brings with it the promise of advanced features, flexibility and expense reduction, which makes it an attractive solution for any company considering installing or upgrading a phone system. Despite all of the attractive attributes of VoIP for business communications, there are risks associated with operating these solutions. In order to make certain capabilities available to remote facilities, teleworkers or mobile employees, certain services have to be exposed publicly in ways that can make securing these systems a more complex endeavor. To put it succinctly, security has the ability to be the enemy of convenience in modern business communications networks.

The migration of voice services onto data networks has significantly transformed the security environment for this category of service. VoIP servers have specific security requirements that, if overlooked, can expose your network to those who would fraudulently route many thousands of minutes of termination to satellite phone carriers in the former Soviet Union at more than five dollars per minute. You do the math.

At a recent conference, the speaker asked the room if anyone had experienced VoIP fraud personally and a man raised his hand to say "My company unknowingly processed nearly $500,000 in fraudulent calls due to a VoIP hack". A number like that should really put the VoIP security issue into perspective.

Unfortunately, public access to VoIP applications is a necessary evil to allow for modern features such as remote device registration or mobile device integration. These features are promoted heavily as additional value in most VoIP solutions and provide great efficiency and control to the companies that utilize them. Considering that the desire for convenience is, at times, diametrically opposed to the requirement for security, how does one make full use of remote capabilities without exposing their network to the opportunity for compromise and fraud?

The following best practices, tactics and technologies can mitigate the risk of fraud while leaving important functionality and capabilities intact. Beyond the obvious firewall restriction of any and all unnecessary services, here are a few of the ways that you can secure your VoIP network without walling it off from remote access by authorized personnel:

Console Login Via SSH is a No-No--SSH access as a method of compromising a server is specific to systems that run on top of a POSIX operating system such as any variant of Linux or Unix. The SSH daemon on your VoIP server(s) should be configured to authenticate only via encrypted key-pair and the service should only be exposed publicly if it is absolutely required.

Strong Password Policies Aren't Optional--The most popular method of hacking IP phone systems and networks is to use automated password cracking applications to "guess" an authorized device's login credentials. Mandate passwords of greater length (eight or more characters) and with sufficient diversity (requiring case, numbers and special characters.)

Route Limitations Can Be a Life Saver--Limit the routes available from your network. If your people don't need to call outside of your local calling area, deny any other routes from termination or implement account codes (password length/diversity important here too) as a second layer of defense against fraud.

Countermeasures Are Your Friend--Use open source software countermeasures on a Linux server to dramatically reduce unauthorized access to your VoIP network. Fail2Ban is a great example of software that watches access attempts to services in your environment, recognizes patterns, and automatically flags fraud attempts as such. Properly configured, software like Fail2Ban can allow you to expose necessary services publicly without opening you up to hackers. As soon as a preconfigured number of bad access attempts are made, the source IP address of the attempt is logged and any future attempt is ignored.

Fraud Mitigation is Worth Considering--The rise of VoIP-based telephony fraud has birthed a number of companies specializing in mitigating this category of fraud. One example of this new type of service provider is Tel-Aviv, Israel-based Humbug Telecom Labs. Humbug offers an affordable subscription service that monitors the traffic patterns and usage across a VoIP network, sends alerts when anomalous activity is detected and can even shut-down services in real-time when fraud is detected.

When you properly implement these and other security protocols in your VoIP network, you can open your systems to remote devices, mobile users and remote administration in good conscience. If you aren't certain of your ability to implement these best practices, find a consultant who can. If you can't find a consultant who can, confine your VoIP network to your LAN and do not expose any of its services publicly. If you do, you just might end up with an unexpected $500,000 phone bill.


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