Social network sites can leave one vulnerable to being humiliated in a public sphere by people unknown to the user.

For cyber bullies, it is a bit of fun, but for the victims it can have a devastating psychological effect.

A recent study has put Australia as the world's worst for online bullying on social networking sites.

One in four Australian students have experienced cyber bullying, a constant barrage of online threats or taunts.

Last May, the state of Victoria criminalised online harassment, after a number of suicides of youths were linked to cyber bullying.

But with no convictions so far, some accuse the police of not taking the crime seriously.

Al Jazeera's Fauziah Ibrahim reports from Melbourne.

Source: Al Jazeera