Jane's Intelligence Review published in March 2014 a good analysis titled "Hashtag Shabaab: Islamists Develop Sophisticated Online Strategy" by Richard Evans, director in the Intelligence, Security and Risk division of IHS Aerospace, Defence, and Security Consulting.
The author concluded that al-Shabaab and its supporters have developed a broad and sophisticated online communication strategy using multiple social media platforms to reach a global audience.
Al-Shabaab has exploited social media to engage with its supporters, adversaries, and the mainstream media, and has successfully shaped the news agenda through micro-blogging platforms such as Twitter.
However, al-Shabaab faces significant challenges in using social media to directly influence people to support its agenda or attract new recruits.
The full article is only available by subscription or access though a library.