US technology companies have become the command and control networks of choice for terrorism, the new head of Government Communications Headquarters, GCHQ has claimed. Robert Hannigan says some US tech companies are in denial about how their services are being misused. He also said UK security agencies needed support from the largest US tech companies which dominate the web. Extremist groups in Syria and Iraq had embraced the web. However, Mr Hannigan says the challenge to governments and their intelligence agencies is huge and it can only be met with greater co-operation from technology companies.