As long as there are people, there will be crimes. India has such harsh punishments for certain crimes. US has the highest conviction rate in the whole world. But, still there are so many crimes that take place.
More people die of road accidents (300 everyday) in India than from any crimes, so you should be more scared about going on a road than about the security in universities. The goal of such people (terrorists) is to instil irrational fear in our hearts, rather than do anything substantial. Their goal is to make people live in fear all the time. If we are allow ourselves to be afraid like this, then they win and we (common people) lose.
In any case, practically, security against such attacks is impractical, if not impossible. Take IIT for example. Do you expect that security people will check the bag of every person entering IIT or to check every car entering IIT? It is impossible. If somebody wants to act stupid and kill people, it is very hard to stop them.