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Denial of Service Attack On Radio Farda's Answering Machines

Radio Farda logo
Radio Farda logo

Radio Farda's answering machines have been flooded with automated phone calls - many looping a speech by Hezbollah leader Nasrallah.

It's nothing out of the ordinary: as Iranian authorities get nervous about potential protests, jamming of Radio Farda's radio programs and website increases (some examples here, here, or here).

But since earlier this week, RFE's Iranian service Radio Farda has experienced a new form of interference from Iran: a flood of automated phone calls aiming to clog up its answering machines.

On an average day, Radio Farda receives between 150 and 200 voice messages from its listeners with everything from eye witness reports to music requests. These messages are recorded by answering machines at RFE's Prague headquarters in the Czech Republic and at its news bureau in Washington D.C.

This Wednesday, RFE's technicians noticed something unusual: a large number of calls coming in from an automated system. Soon, Radio Farda's answering machines were receiving 200-300 calls an hour - an obvious attempt to block out regular callers with a variation of a "dial of service," or DoS attack.

Upon connection, these calls played just over 1 minute of a looped recording of speeches and sermons in Farsi before hanging up. In a slightly unexpected twist, yesterday this changed to a loop of a recent speech by Hezbollah leader Hassan Nasrallah.

As of today, the automated calls are continuing. RFE's technicians are making sure that regular callers can get through. The service was never interrupted.

Like other international broadcasters, RFE has observed intense jamming of its Persian radio and satellite broadcasts in recent weeks. Radio Farda's website is also routinely blocked. Despite this aggressive censorship, Radio Farda's website has seen an approximate 50% increase in web traffic over the past two weeks, including through proxy servers, which allow users in Iran to surf the web anonymously. Ever since the protests following the 2009 Presidential elections, record numbers of Iranians have turned to Radio Farda.