The greatest threat to global security is the rapidly increasing number of failed states. Even though there is no agreed-upon definition of a failed state, it is generally understood that when a government can no longer provide basic security to its people due to a rise in violence or extreme poverty, or loses control over part of its territory to domestic or foreign terrorist groups, the state has failed.

A major reason to be concerned about the increasing number of failed states is that they are natural breeding grounds for local or international terrorists. And given the increasing proliferation of weapons of mass destruction, including chemical and nuclear, the more failed states, the higher the probability of the bad actors being able to develop or acquire very lethal weapons. All of this leads to an increased probability of terrorists hitting targets in Europe, the United States and elsewhere.
There are failed states such as Haiti and Guinea-Bissau, resulting from decades of mismanagement and rampant corruption, which have left their populace in poverty. Those countries are a humanitarian tragedy, but provide little security danger to the rest of the world. Of much greater concern are failed states that threaten the world around them. Somalia has been a failed state for several decades, causing it to be a breeding ground for radical Muslim terrorists and pirates, who plague shipping along the east coast of Africa.