In a written argument to the Investigatory Powers Tribunal (IPT), cited by the Guardian, GCHQ rejected claims brought by Privacy International and seven internet service providers that its hacking activities were disproportionate and illegal.
“GCHQ and other intelligence agencies must develop innovative and agile technical capabilities to meet these serious national security challenges. Computer Network Exploitation is one such capability," GCHQ said, adding that CNE sometimes is "the only way to acquire intelligence coverage of a terrorist suspect or serious criminal in a foreign country.”
It denied that it was engaged in any unlawful and indiscriminate mass surveillance activities, adding that the British legal regime provides “stringent safeguards” for CNE activities.
Privacy protection in the United Kingdom is a hotly debated topic following US whistleblower Edward Snowden leak of classified information in 2013, including revelations of mass surveillance of personal data by GCHQ together with the National Security Agency (NSA) of the United States.