Here is some real useful info:

What is an Internet Troll?

An Internet "troll" is a person who delights in sowing discord on the Internet. He (and it is usually he) tries to start arguments and upset people.

Trolls see Internet communications services as convenient venues for their bizarre game. For some reason, they don't "get" that they are hurting real people. To them, other Internet users are not quite human but are a kind of digital abstraction. As a result, they feel no sorrow whatsoever for the pain they inflict. Indeed, the greater the suffering they cause, the greater their 'achievement' (as they see it). At the moment, the relative anonymity of the net allows trolls to flourish.

Trolls are utterly impervious to criticism (constructive or otherwise). You cannot negotiate with them; you cannot cause them to feel shame or compassion; you cannot reason with them. They cannot be made to feel remorse. For some reason, trolls do not feel they are bound by the rules of courtesy or social responsibility.

Why does it Matter?

Some people -- particularly those who have been online for years -- are not upset by trolls and consider them an inevitable hazard of using the net. As the saying goes, "You can't have a picnic without ants."

It would be nice if everybody was so easy-going, but the sad fact is that trolls do discourage people. Established posters may leave a message board because of the arguments that trolls ignite, and lurkers (people who read but do not post) may decide that they do not want to expose themselves to abuse and thus never get involved.

Another problem is that the negative emotions stirred up by trolls leak over into other discussions. Normally affable people can become bitter after reading an angry interchange between a troll and his victims, and this can poison previously friendly interactions between long-time users.

Finally, trolls create a paranoid environment, such that a casual criticism by a new arrival can elicit a ferocious and inappropriate backlash.

The Internet is a wonderful resource which is breaking down barriers and stripping away prejudice. Trolls threaten our continued enjoyment of this beautiful forum for ideas.

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The Webmaster's Challenge

When trolls are ignored they step up their attacks, desperately seeking the attention they crave. Their messages become more and more foul, and they post ever more of them. Alternatively, they may protest that their right to free speech is being curtailed -- more on this later.

The moderator of a message board may not be able to delete a troll's messages right away, but their job is made much harder if they also have to read numerous replies to trolls. They are also forced to decide whether or not to delete posts from well-meaning folks which have the unintended effect of encouraging the troll.

Some webmasters have to endure conscientious users telling them that they are "acting like dictators" and should never delete a single message. These people may be misinformed: they may have arrived at their opinion about a troll based on the messages they see, never realizing that the webmaster has already deleted his most horrific material. Please remember that a troll does have an alternative if he has something of value to say: there are services on the net that provide messaging systems free of charge. So the troll can set up his own message board, where he can make his own decisions about the kind of content he will tolerate.

Just how much can we expect of a webmaster when it comes to preserving the principles of free speech? Some trolls find sport in determining what the breaking point is for a particular message board operator. They might post a dozen messages, each of which contains 400 lines of the letter "J". That is a form of expression, to be sure, but would you consider it your duty to play host to such a person?

Perhaps the most difficult challenge for a webmaster is deciding whether to take steps against a troll that a few people find entertaining. Some trolls do have a creative spark and have chosen to squander it on being disruptive. There is a certain perverse pleasure in watching some of them. Ultimately, though, the webmaster has to decide if the troll actually cares about putting on a good show for the regular participants, or is simply playing to an audience of one -- himself.