The US electronic spying chief has said massive surveillance programmes newly revealed by an ex-intelligence worker had disrupted dozens of terror plots.
In a US Senate hearing, National Security Agency ( NSA) Director Keith Alexander defended the internet and telephone data snooping programmes.
Also, US Secretary of State John Kerry said they showed a “delicate but vital balance” between privacy and security.
The programmes were revealed in newspaper accounts last week. Meanwhile, the leaker has pledged to fight extradition to the US.
Edward Snowden fled his home in Hawaii for Hong Kong shortly before reports of the top secret programmes were published by the Guardian and Washington Post newspapers last week.
The 29-year-old former CIA and NSA contract worker has admitted giving the newspapers information about NSA programmes that seize vast quantities of data on telephone calls and internet communications from US internet and telephone companies.
US officials have confirmed the programmes exist, with President Barack Obama saying they were closely overseen by Congress and the courts.
‘Americans will die’
European leaders have expressed concerns over the scale of the programmes and have demanded to know whether the rights of EU citizens had been infringed.
Meanwhile, in a news conference alongside UK Foreign Secretary William Hague in Washington DC, Mr Kerry also said the programmes had “prevented some pretty terrible events.”
“With respect to privacy, freedom and the Constitution, I think over time this will withstand scrutiny and people will understand it,” he said.
Source: Standard Digital