Apple is issuing a security update after powerful spyware was found targeting an activist's iPhone in the Middle East.

Computer forensics experts said the software takes advantage of three previously undisclosed weaknesses in Apple's mobile operating system, allowing hackers to take complete control of iPhone handsets.

Reports published by the San Francisco-based Lookout and internet watchdog group Citizen Lab outline how the spyware could compromise an iPhone with the tap of a finger.

Apple said in a statement that it had fixed the vulnerability as soon as it heard about it.

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