With the introduction of VoIP, you can use the internet to make telephone calls instead of relying on a separate telephone line. However, the technology does present security risks.
Voice over internet protocol (VoIP), also known as IP telephony, allows you to use your internet connection to make telephone calls. Instead of relying on an analog line like traditional telephones, VoIP uses digital technology and requires a high-speed broadband connection such as DSL or cable. There are a variety of providers who offer VoIP, and they offer different services. The most common application of VoIP for personal or home use is internet-based phone services that rely on a telephone switch. With this application, you will still have a phone number, will still dial phone numbers, and will usually have an adapter that allows you to use a regular telephone. The person you are calling will not likely notice a difference from a traditional phone call. Some service providers also offer the ability to use your VoIP adapter any place you have a high-speed internet connection, allowing you to take it with you when you travel.
Because VoIP relies on your internet connection, it may be vulnerable to many of the same problems that face your computer and even some that are specific to VoIP technology. Attackers may be able to perform activities such as intercepting your communications, eavesdropping, taking control of your phone, making fraudulent calls from your account, conducting effective phishing attacks by manipulating your caller ID, and causing your service to crash (see Avoiding Social Engineering and Phishing Attacks and Understanding Denial-of-Service Attacks for more information). Activities that consume a large amount of network resources, like large file downloads, online gaming, and streaming multimedia, may affect your VoIP service.
There are also inherent problems to routing your telephone over your broadband connection. Unlike traditional telephone lines, which operate despite an electrical outage, if you lose power, your VoIP may be unavailable. VoIP services may also introduce problems for location-dependent systems such as home security systems or emergency numbers such as 911.
Author: Mindi McDowell Produced 2005 by US-CERT, a government organization. Terms of useLast updated November 15, 2010 
