During the last decade the greatest terrorist threat has come from what is referred to as ‘jihadist terrorism’. Certainly, since 11 September 2001, many bloody terrorist attacks have been carried out under the pretext of a religious armed struggle, known as the ‘jihad’. The NCTb already established, at the start of 2007, that jihadists were using the Internet widely as a resource for propaganda, for example, or to recruit people. The NCTb also investigated the threat of terrorist attacks against the Internet (Internet as a target) or via the Internet (Internet as a weapon). Both the Internet and jihadism are continuing to develop. That is why it became necessary to review the original assessment of the threat in the form of this ‘2009 update’. After all, the government and private parties cannot afford to relax and let developments simply run their course. Therefore, since the publication of the earlier study at the beginning of 2007, numerous measures have been taken to counteract the threat based on Internet use by jihadists. Although this study shows that the threat has not substantially changed, the findings in this study provide useful guidelines on how to continue to respond adequately to the threat.