Fears raised over terrorist threat via VoIP

Police have outlined their concern that terrorists could be making use of VoIP services to communicate without being traced.

Traditional phone tapping techniques which are effective on landlines and mobile phones are less useful on internet telephony technology, experts told Sky News.

Intelligence officials may be able to see that a conversation is taking place, but it is more difficult to tell who is speaking, where in the world they are and listen in on what they are saying.

Peter Sommer, an authority in the use of new technologies in crime, told the news network: "The problem for law enforcement is you can issue a warrant but you may not be able to enforce it against the company because the company is overseas.

"If you can enforce it, you have still got no idea where the person is who is making the call - if you get hold of the content, it is going to be encrypted and you are not going to be able to decrypt it."

However, sources told Sky that "huge investment" was being put into cracking this problem by police and intelligence services - despite legal moves in the courts to make tapping of any sort more difficult.