They lurk in the comments sections of websites, firing off inflammatory messages behind a cloak of anonymity.
"Comment trolls," as they're called, are the scourge of many a news site or blog seeking to make their comments section a forum for intelligent discussion.
Amid a growing debate among US newspaper editors over the practice of allowing anonymous comments, one New York publication is taking a stand.
The Buffalo News announced on Monday that it will begin requiring identification from people who want to leave comments on its website, BuffaloNews.com.
"We will require commenters to give their real names and the names of their towns, which will appear with their comments, just as they do in printed 'letters to the editor,'" Buffalo News editor Margaret Sullivan said.
Websites have employed a variety of methods to deal with "trolling" - from banning comments altogether to deploying filtering software which screens out posts containing profanity.
Some websites, including The New York Times, have comments vetted by human editors or moderators before allowing them to be posted online.
Others require users to supply an email address before being allowed to comment or rely on readers to flag inappropriate comments so they can be removed.
With a weekday circulation of more than 162,000 and a Sunday circulation of over 244,000, the Buffalo News is believed to be among the first major US newspapers to require that a comment carry a real name.
Sullivan, in a column explaining the move, said the decision to require identification was taken "after quite a bit of internal discussion" and would begin in August.
"Online commenting began, a year or so ago, as a way to engage our Web readers and give them a chance to air their points of view and get some discussion going on the topics of the day," Sullivan said.
"Quickly, though, the practice degenerated into something significantly less lofty," she said. "Reader comments can be racist and ugly."
Dan Kennedy, an assistant professor of journalism at Boston's Northeastern University, said the Buffalo News may be the first of many news sites to crack down on anonymity.
"I think we're going through a period where a lot of people are starting to rethink anonymous comments," Kennedy told AFP. "A lot of people are thinking about this and talking about this."
Rem Rieder, editor of the American Journalism Review, welcomed the move by the Buffalo News, which coincided with a column he wrote in the latest edition of the magazine calling for an end to anonymous comments.
"The opportunity to launch brutal assaults from the safety of a computer without attaching a name does wonders for the bravery levels of the angry," Rieder said.
He pointed out that while the websites themselves are generally immune from prosecution, a number of news outlets have encountered legal problems because of allegedly defamatory comments posted by anonymous users.
"Continuing to allow anonymous sniping hardly seems to be in the self-interest of news outlets," Rieder said. "There's just no defense for a system that allows anyone to post this kind of stuff anonymously."
The Buffalo News announcement drew a mixed reaction in the comments section on its website with some readers welcoming the move and others denouncing it.
"Yeah! It's about time some changes were made," wrote a user identified only as "itsme." "All the little trolls and bullies can go away now."
Others felt the new rules would drastically reduce participation.
"I don't like the idea of using my real name on sites such as this because there are a lot of loonies out there," said "Justathought26."
"There goes free speech and honest criticism," added a user with the handle "tommyd."
"The online version of the News, just like the paper version will soon die and go away."