They plan hits that send the highest level of shockwaves in any otherwise calm society that hardly suspects it is a target for attack.
After a rather lengthy experience with terror, one can assume that it is now easy to fight the scourge. It is safe to assume that every major event in any country is a potential occasion for terrorists to strike.
Such was the sad awakening for the Americans at last year's Boston Marathon. The Bostonians and Americans at large though, refused to be cowed by bombings and held this year's edition of the event peacefully although of course, it was hard to forget what happened just a year back. No one is safe from terror attacks because basically it is a war without a visible enemy.
That is perhaps one of its strongest points but also its weakest. The terrorist wants to declare very clearly and loudly his presence but not be visible. Even the Westgate attackers in Kenya in the end did not want to be visible.
In my opinion, it is useless to always blame Al Qaeda or Al Shabaab. True, those are perhaps the most notorious terrorist organizations but as the Americans learned last year, there is now the threat of home grown terrorists.
I think every country has to be very vigilant against its radicalized citizens and home grown terrorists because that is perhaps terrorism's best achievement and next level in its overall scheme of things to have the whole world kneel to its authority and power.
Thus, it was both shocking as it was consoling when President Jakaya Kikwete went public in a recent media interview that Tanzania helped foil terror attacks meant to disrupt Kenya's last general election and the swearing-in ceremony of the neighbouring country's national leaders.
Such matters are indeed rarely mentioned in public but the President certainly had very good reasons and also a clear message for all when he decided to go public. The message is that although East Africa has expansive borders, the region is not as porous as some people would want to believe.
His reasons are clear. The President wanted to tell everybody that the war against terror has to be carried out by all citizens of the region. Of course terror inflicts grievous damage due to its awesome machinery to kill and maim but beyond that, it is highly doubtful that it can bend the resolve of society to fight back.
Like the President said, formerly, terror was an alien war, something that involved Americans against their trail of global enemies. But things have changed. Terrorists fight everyone and everybody.
Mao Zedong defined war as a continuation of politics. With terror however, it is hard for people of goodwill to propose points for engagement in dialogue because basically, there is no politics to talk about.
So the world goes on with a problem unique for the 21st century. I believe East Africa shall always be a safe place for citizens and visitors alike because for centuries the people of this region refused to embrace the culture of violence as our dominant and defining character.
Our resolve for peaceful existence is also exemplary and that is why East Africans should thank President Kikwete for reminding us to be vigilant and permanently on alert.