"In Internet terminology, a
TROLL is a person who enters an established community such as an online discussion forum and intentionally tries to cause disruption, often in the form of posting messages that are inflammatory, insulting, incorrect, inaccurate, or off-topic, with the intent of provoking a reaction from others. Trolls can also be existing members of such a community that rarely post and often contribute no useful information to the thread, but instead make argumentative posts in an attempt to discredit another person, more often than not based on what they thought was said rather than what was actually said by the other person, concentrating almost exclusively on facts irrelevant to the point of the conversation, with the intent of provoking a reaction from others. The latter are primarily, though not always juveniles from other countries who don't have enough understanding of the language to realize that there is nothing to argue about, the points are truly irrelevant to the conversation, or they just don't care and are simply trying to cause the other poster grief with their frivolous and irrelevant arguments."
Pretty much sums it up, doesn't it?
See also
Ad Hominem: "An ad hominem argument, also known as argumentum ad hominem (Latin: "argument to the person", "argument against the man") consists of replying to an argument by attacking or appealing to the person making the argument, rather than by addressing the substance of the argument. It is most commonly used to refer specifically to the ad hominem abusive, or argumentum ad personam, which consists of criticizing or personally attacking an argument's proponent in an attempt to discredit that argument."
Textbook!
(Ref: Wikipedia)