An internet 'troll' was jailed yesterday for the maximum sentence of 18 weeks for posting abusive and upsetting messages on social networks.

Sean Duffy posted on tribute pages to several teenagers who had recently died or committed suicide, causing upset for bereaved friends and relatives. He did not know any of his victims.

Duffy even went as far as uploading to YouTube. Following the death of Natasha MacBryde, 15 who was hit by a train, he posted a video called "Tasha the Tank Engine" with the girl's face superimposed on the body of the animated character. He also posted a number of comments on the Facebook tribute page created by her brother James which were clearly designed to upset.

“He has now been exposed for what he is: a very twisted individual. I hope his sentencing shows other trollers that they are not anonymous and they will be caught if they continue their vile games.” said Natasha's father, Andrew MacBryde.

The unemployed man, who suffers from Asperger's Syndrome and lives alone, pleaded guilty to two counts of sending malicious communications. He has also been served with an ASBO (Anti Social Behaviour Order) which prohibits him from accessing any social media websites for five years.

The use of the term 'troll' and 'trolling' refers to messages posted on internet forums by anonymous users specifically created to antagonise and provoke an emotional response from other users. The imprisoning of Sean Duffy has sparked debate online about whether this restricts the freedoms of the internet.