VoIP Phone Vulnerabilities

At the IP’06 event in London recently, I heard Tom Cross of Internet Security Solutions present on VoIP Security, and some of types of threats to VoIP phones.  Those of you that have listened to the Bluebox Podcast will have heard Dan York, Jonathan Zar and Shawn Merdinger talk about the threats to phone handsets before.  Some of these devices ship from the factory in an unsafe state, with security holes like remote configuration backdoors and TFTP servers running on the phone.  Often if there are usernames and passwords they can be weak combinations like ‘1’ and 1′ or ‘root’ with no password.  Often users do not know that these back doors are open, and the software does not force you to change from default or factory passwords.

The cost of not closing these security holes is that someone could remotely hack into the phone, and once in control of the phone could trace or record phone calls; mount a denial-of-service attack such as repeatedly reboot the phone; or hijack the phone in order to make calls at your cost.  So Tom’s advice was to make sure that VoIP phones are not accessible to the Internet, so they can’t be attacked from outside.

In many ways the PBX is a dinosaur these days, since it is solving problems we no longer have.  For example VoIP phones have built in dialling directories, so we don’t need a special abbreviated dialling system inside the company; VoIP softphones can have their own voicemail functionality, so we don’t need the PBX to do that.  Also traditionally, the PBX has been the device that shares out and manages the expensive, limited resources, the telco trunk lines, and increasingly PBXes don’t need to do that either, often sitting just on a LAN or LANs.  However, thinking about Tom’s words, the security aspect is a whole new reason to buy PBXes, as any device that can limit the exposure of SIP phones to attack is going to be of benefit.