According to the SITE Intelligence Group, a private company that monitors online jihadist traffic,the threat comes from Umar al-Basrawi, a frequent contributor to a major Islamic jihadist forum.
http://www.stripes.com/blogs/stripe...-for-muslims-to-kill-david-letterman-1.152422
http://www.stripes.com/blogs/stripe...-for-muslims-to-kill-david-letterman-1.152422