In terrorism prevention and in the investigation of suspected terrorist plots, which are by their very nature clandestine, there is little doubt that the acquisition, analysis and use of information about terrorist groups by intercepting communications and by other means of electronic surveillance are essential tools to pursue legitimate and vital objectives, namely the protection of lives and national security as well as securing justice for victims of terrorist attacks. The intelligence community generally focuses on terrorism prevention, whereas law enforcement officials are primarily concerned with bringing any alleged perpetrators to justice though an element of their role is inherently preventative in nature also.
With developments in modern technology a wide array of investigative techniques lies at the disposal of law enforcement agencies when combating terrorism. The continuous technological innovation further enables governments to use more intrusive techniques for monitoring individuals' activities. The persons in question, however, may have fewer opportunities to know or to detect that they had been placed under surveillance. To illustrate, before the advent of modern technologies government agencies relied mainly on recruiting informants and on sending undercover agents to gather information about an individual. Law enforcement and intelligence services used to distinguish between covert and overt intelligence. The distinction was based on how much contact a government agent had with the target. Modern surveillance technologies have erased this distinction. One now discusses surveillance in terms of its function, namely to collect information and to monitor the behaviour of individuals (UNODC, 2009, p. 2).
Modern technologies allow the government agents to penetrate many aspects of an individual's life. This can take many different forms, such as the utilization of hidden miniature cameras; (UNODC, 2009, p.2) the employment of facial recognition software to establish the identities of individuals captured on the video surveillance system through linking the video footage to a database containing the photographs of citizens (Pettit, 2017); the utilization of software to identify suspicious activities based on the captured video surveillance in public places (Mallonee, 2017); and various forms of tapping and recording devices such as forwarding conversations made through a voice over the Internet protocol to a special server; the monitoring of an individual's movement through placing a global positioning system device on a vehicle or through monitoring an individual's mobile telephone; or the accessing of files stored on a computer and the intercept of communications sent over the Internet (UNODC, 2009, p.2). These are not necessarily unlawful in and of themselves, so long as they are accompanied by appropriate and adequate accountability and review mechanisms as well as meeting the legal requirements of privacy described earlier.
Despite the significant benefits that such technologies bring, including in terms of counter-terrorism prevention, there are also important accompanying concerns regarding the impact that such measures may have on the enjoyment of human rights, in particular the right to privacy. The European Court of Human Rights (ECtHR) has warned of "the risk that a system of secret surveillance for the protection of national security may undermine or even destroy democracy under the cloak of defending it" ( Weber and Saravia v. Germany, 2006, para. 106).
One particular issue that can arise in relation to international cooperation on intelligence sharing is where States cooperate with other States with weaker data protection legislative safeguards and intelligence oversight mechanisms to collect and transfer intelligence which may be unlawful for State organs of their own country to gather. Such practices risk undermining the essence of the right to privacy and the requirement of lawfulness (OSCE, 2011, para. 5).
Another separate, though often related, area of concern is regarding the effect of poorly drafted, often vague and overly broad, anti-terrorism legislation, including of their accompanying definitions of key concepts including 'terrorism' or 'organised criminal group'. This can facilitate otherwise impermissible interferences with the privacy of individuals or organizations (United Nations, OHCHR, 2017).