no one has claimed responsibility for is bombing. There was 21 killed and 25 hurt. The bomber targeted a Shia mosque in the city's northeast al Harithyia neighborhood.
what should we do to try and prevent this attacks?
As heartless as this may sound, people are killed every single day like this. Yes, I do think something should be done about this, but who is to say we aren't doing something about it right now.
The United States assault on ISIS is not only meant to stop them but to paint the message of "we will hunt you down and stop you." With that message, I don't think many other groups of terrorists will be eager to engage in such horrible crimes. Whether our actions against ISIS are effective or not is another story. Personally, I believe we need a more direct/more powerful attack against ISIS. In order to achieve this message, we need to be effectively stopping ISIS. Just my thoughts.
Dylan is right, in the US such an attack would be seen as shocking, sadly in Iraq these types of attacks have become all to common. The attack targeted Shia, so I don't know if there is much we can do. This kind of factional fighting between Muslims is almost as old as Islam itself. Hopefully radicalism will die as the Middle East develops.