Interoperability and confusion over who is responsible for security are causing problems in implementing VoIP. IT administrators say that the lack of security in VoIP is a major concern for them according to experts speaking at the VON Europe conference.

The technology and standards that exist to secure VoIP are not the issue, said Tim Jasionowski, senior technologist for voice and rich media technologies at Nokia. The problem is that most enterprises aren't using many of the technologies.

That's mainly because unless an enterprise uses a single vendor for every piece of equipment in their network, including phones, IP-PBX (IP-private branch exchange), firewall and all other components in between, then security technologies such as TLS (Transport Layer Security) and others are unlikely to interoperate across multi-vendor equipment, he said.

Even if an enterprise decided to standardise on a single vendor, it might have additional limits on the products it chooses. That's because not all major vendors are building support for security standards like TLS into their products and those that do don't necessarily support it across their entire product range, said Cullen Jennings, distinguished engineer at Cisco Systems.

Once enterprises decide to extend VOIP into mobile devices, they face additional problems, but once again not because the standards and technology doesn't exist. Ideally, an enterprise might want to run WPA (Wi-Fi protected access) to secure the Wi-Fi connection on a wireless device, an authentication mechanism for users that may attach to public hotspots, a VPN for accessing the corporate network and possibly other security techniques.

"That's great if you have a nuclear power plant in your pocket attached to your mobile phone," Jasionowski said. Running all of those security applications requires processing and power, both features in short supply on mobile devices.

In addition, the market hasn't fully worked out who exactly is responsible for security and who is responsible for enforcing that security, said Ari Takanen, chief technology officer for Codenomicon. Currently, layers of security are offered by service providers and equipment makers and sometimes their efforts overlap. Without the clarity of claimed responsibility, no source is liable for security issues, he said.

Enterprises can improve their chances of being able to boost the security on their VoIP networks in a couple of ways, including carefully examining the type of tests that vendors say they run on their products to make sure they work, Takanen said. Organisations like the Protos Project, a collaboration between the Finnish University of Oulu and VTT Electronics, can help buyers test products, he said.

In addition, enterprises are responsible for demanding that vendors interoperate, Jasionowski said. In the meantime, product managers are making decisions against interoperability against the advice of their engineering staffs in hopes of securing more business, he said.