If computers have the ability to communicate then it is possible for students to find ways of sending messages even if we disable facilities such as email. Although it is not a complete solution, the examination computers should have the standard communication programs removed. Traffic between computers in the laboratories should be disabled or at least monitored. The solution to the communication problem needs to be mainly non-technical. The severity of the offence has to be emphasised and instances where it is detected should result in severe penalties such as an automatic fail of the subject.
Supervision has to be increased with regular monitoring of both screens and traffic.
Consideration should be given to allowing students to anonymously report other students whose behaviour is questionable during the examination. From the questionnaire responses and from informal discussions with students it seemed that there was an unacceptable degree of communication between some students. In practise it might not advantage many students. My impression is that poorer students were the only ones attempting to communicate and these students tended to send the incorrect answers. In an open book examination prewritten answers are always a possibility.