http://www.telegraph.co.uk/news/worldnews/middleeast/iran/8388484/Iran-crack... Iran cracks down on web dissident technology Iranian security authorities have launched a new crackdown on dissidents online by blocking US government-backed technology that allows them to speak out safely. Tor took off in Iran after the disputed 2009 election Photo: AFP/GETTY By Christopher Williams, Technology Correspondent 7:00AM GMT 18 Mar 2011 Internet freedom activists believe the regime in Tehran has implemented highly sophisticated internet surveillance technology and that an information b arms raceb is now inevitable. The crackdown targeted Tor, a free piece of software that allows anyone to connect to internet via a global private network that hides computer IP addresses, which could be used by authorities to identify and locate dissidents. It also encrypts the contents of users' internet communications, making eavesdropping on emails, Facebook, Twitter and other applications more difficult. On average, around 250,000 computers worldwide are connected to the Tor network at any time, making it the leading anti-surveillance technology online. But in mid-January, as revolutionary fervour swept the Middle East, the number of computers connected to the Tor network via one major Iranian broadband provider collapsed almost overnight from more than 11,000 to zero. Investigations by the Tor Project, the not-for-profit company that runs the system, have since revealed that, crucially, other encrypted traffic such as internet banking was still flowing. It meant Iranian authorities had for the first time found a way to identify and block only Tor connections, and therefore a way to potentially identify dissidents. b What they did was vastly upgrade their capability,b said Andrew Lewman, executive director of the Tor Project. The technology responsible for the new threat was Deep Packet Inspection (DPI), a type of high-end network equipment that uses ultra-fast microchips to read and classify internet traffic in transit. The Iranian authorities used DPI to detect the highly specific parameters Tor uses to establish an encrypted connection. b From an engineering perspective this is fantastic,b said Mr Lewman of his adversaries' efforts. He added that the Tor Project had known it could be attacked in this way b for yearsb , but had chosen not to take pre-emptive measures because b webre trying to have an arms race really slowlyb . In the last few weeks developers have redesigned the software so that its traffic looks just like any other when it sets up an encrypted connection, and Iranian user numbers are now back to normal. It is unknown who supplied Iran with the DPI technology, but few technology manufacturers build equipment capable of reading and classifying internet traffic at the necessary scale and speed. Last year, Nokia-Siemens faced a European Parliament hearing after it admitted selling a mass communications b monitoring centreb to an Iranian mobile network. b Who knows, maybe they just got someone to configure it for them,b Mr Lewman speculated. Whoever the supplier, the temporary block on Tor does show that Iran is now more advanced than even China and its Great Firewall in terms of the technology it uses to suppress dissent online, said Mr Lewman. The regime has rapidly caught up with its critics since the unrest following the 2009 election, when the number of Tor users rocketed from approximately 1,200 to 2,800 in a matter of days as many Iranians first began to use social networks to organise protests. The value of b internet freedomb technologies to US foreign policy has not gone unnoticed in Washington: the Tor Projectbs arms race with Iranian authorities is funded in part by grants from both the Department of Defense and the State Department.