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Hold the IP Phone: Page 2 of 7

A key area to consider when choosing a PBX is the underlying OS. IP-based PBXs come in two basic flavors, closed and open. Those built around proprietary architectures are considered closed, while systems built on off-the-shelf PCs and OSs are open. For example, Alcatel's systems use Unix or Linux; AltiGen, Avaya and Cisco Systems use Windows; 3Com Corp. and Mitel Networks Corp. use Wind River Systems' VxWorks; and NEC Corp. and Siemens run proprietary OSs (for in-depth reviews of telephony products, see www.commweb.com).

Each type has pros and cons. First, with closed PBX architectures, everything comes from one vendor, meaning you'll have only one company to contact when you encounter problems. Combining components from multiple vendors can make for complex, hard-to-maintain systems and possible security breaches caused by interoperability troubles. Because closed systems don't use off-the-shelf OSs, someone trying to hack into a closed PBX will have to spend time learning about the OS and how it operates. As always, applying any and all security patches for your PBX OS, whether open or closed, is important. On the plus side for open systems, security patches may become available quicker than they will for closed architectures, lessening the time you may be vulnerable.

Keep Your Eyes Open

Monitoring is a must for you to maintain the security of your IP PBX. Get accustomed to examining reports on a regular basis--don't become complacent. Reports are the early warning system that alerts you to possible problems. They can flag not only suspicious IP traffic, but also calls that shouldn't be going through the system.

Scrutinize the reports every day, seeking not only blatantly suspicious calls, such as those to foreign countries and those that occur when people should not be in the office, but also subtler anomalies, such as an excessive number of calls from one extension. Look for calls to locations beyond the normal calling area, as well as those that last longer than usual. And consider using IP PBXs, like 3Com's NBX, available through the Network Supervisor add on, that include a real-time alarm-forwarding feature that can alert you to calls outside the expected norm for length and destination.