In Iran, there's a monumental battle going on in cyberspace at the moment between the censors of information and citizens who want to know what's going on.

Just like in Burma in 2007 and in China earlier this year, the authorities in Iran are blocking full access to the internet and sites like YouTube. In Iran, at the moment, the internet is functioning but limited with some sites blocked.

The Iranian authorities are also using something called deep packet inspection or DPI which basically allows network operators or a government to intercept data on the internet and deconstruct it to search for particular keywords and then block the communication.

Telecoms dilemma

But for companies selling such equipment there's a dilemma. They say monitoring is part of any normal phone or internet network - it's what the owners have to be able to do.

Ben Roome of Nokia Siemens Networks, for example, says a "monitoring centre" installed within the Iranian government's telecoms monopoly was a normal part of any phone network.

Beating censorship

There are companies which try to find ways of defeating the censors.

Rafal Rohozinski is the chief executive of Psiphon, which is one such company.

He's based in Ottowa and is the principal of the SecDev Group which is associated with a venture involving Cambridge University in England and Harvard in the United States.

First broadcast on 24 June 2009