The British secret service GCHQ used the iPhone of suspects to spy on them, the smartphone started to send data to the British agency when it was connected to an infected computer. The German website Der Spiegel reports the method was found in documents of whistleblower Edward Snowden.
GCHQ would have been unable to get access to the iPhone itself but instead downloaded data from the phone when it was connected to an infected computer. Using this method it was not required to hack the security of the iPhone. The British secret service also used the UDID, an unique number which could be used to identify a iPhone and iPad. The UDID could also be read when the iPhone was connected to the infected computer. With the UDID the internet behaviour of the suspect could be tracked.
GCGQ abused a vulnerability in Safari and information from Google’s mobile advertising network Admob. With the method the UDID could be tracked and the secret service could follow what websites the iPhone user visited and what he searched for on the internet.
The concerned GCHQ document was written in 2010 and it’s likely the described method no longer works. Since 2012 Apple no longer allows apps in the App Store that require the UDID.