This article explores the evolution and links of the Somali-based Islamist terrorist group, Harakat al-Shabab al-Mujahedeen (more popularly known as al-Shabab-'the youth'). It argues that al-Shabab's attack on the Westgate shopping mall in Kenya should be understood in the light of the group's deepening ties with al-Qaeda and its espousal of the latter's global jihad campaign. In addition, the article argues that the Westgate attack and other atrocities fundamentally demonstrate al-Shabab's willingness and increased capability to hurt targets outside its traditional Somalian base. It also suggests that the group is moving away from insurgent activity in Somalia itself and has mutated as a transnational terrorist movement, with grave consequences for regional and international security.