Re:UK spies using social media data for mass surveillance
by lostboys67 on Wednesday October 18, 2017 @09:39AM
(#15499009)
but there are also protections e.g. if they come across evidence of stuff that is not related to national security it is ignored.
It's all laid out in section 28 of the DPA: https://www.legislation.gov.uk/ukpga/1998/29/section/28