IF YOU’VE BEEN SLIMEDWhom to sue: Under Section 230(c) of the Communications ­Decency Act of 1996, website ­operators have immunity, so you can’t sue a message-board host; however, it may be possible to go ­after the commenters directly and find out their identity during the litigation process.

What to claim: If suing for defamation, it’s imperative to show that someone made a false statement that has damaged you, generally by harming your reputation. If you’re a public figure, you need to show “actual malice”—that the comment was made with knowledge that it was false or at least with recklessness as to its truth. (You might also have claims for violation of privacy, copyright infringement, or intentional infliction of emotional distress.)

IF YOU’RE THE COMMENTERIf you’re hidden: The plaintiff may send a subpoena to the website administrator or your internet service provider seeking to learn your identity. You can respond with a motion to quash the subpoena, arguing that your First Amendment right to free speech outweighs the plaintiff’s interest in unmasking you.

If you’re outed:

* Show that the statement is true.

* Argue your comment was just an opinion (a defamatory statement must be factual).

* Claim your statement was clearly satire, parody, or hyperbole, which no reasonable reader would take seriously. The frequency with which schoolyard insults and locker-room epithets fly on the internet may help you in this regard.