The first known lawsuit against instant-message spam, sometimes called “spim”, was announced on Thursday by America Online as part of a campaign to stem unwanted computer messages.

AOL, a unit of Time Warner and a major provider of real-time instant-messaging, said it targeted 20 “John Doe” defendants in the first lawsuits against instant-message spam.

The announcement came as part of a series of lawsuits against unwanted email messages, or spam, by AOL and other providers including Microsoft, EarthLink and Yahoo.

AOL said it filed its first legal action targeting a spammer peddling controlled substances, including the pain reliever Vicodin and other pharmaceuticals, which require a physician’s prescription.

AOL and the others sued under the new CAN-SPAM law that went into effect this year, but which analysts say have done little to stem the tide of spam.

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