The latest film from documentarian Alex Gibney attempts to reveal the story behind the Stuxnet computer virus (described as “the most sophisticated malware virus ever seen”), but finds itself thwarted by layers of classified information and some slightly creaky stylistic devices. What we learn in this informative but occasionally repetitive film is that the virus, a self-replicating worm first identified in 2010, was created by the CIA in order to sabotage Iran’s nuclear programme. And that cyber weapons should be taken every bit as seriously as nuclear and chemical devices. Be very afraid.