An ICSR report 'Who Matters Online: Measuring influence, evaluating content and countering violent extremism in online social networks' by J.M. Berger & Bill Strathearn. Fifty-three pages and in the summary ends with:
Finally, we believe that these metrics are only a starting point for the study of extremist use of social media. We believe the metrics and approaches here can be further refined, and we believe that additional research may yield substantial new
techniques for monitoring and countering the promotion of violent ideologies online.
Link:http://icsr.info/wp-content/uploads/...Strathearn.pdf