Four of the nation's largest online providers yesterday announced a new round of lawsuits aimed at e-mail spammers, including the first major case involving spam sent via an instant messaging service.

America Online Inc., Yahoo Inc., Earthlink Inc. and Microsoft Corp. all filed suits in federal courthouses around the country, alleging violations of the federal anti-spam law passed late last year and of state statutes.

AOL filed two suits in U.S. District Court in Alexandria, one targeting 10 unidentified people who allegedly used e-mail to market the painkiller Vicodin and other pharmaceuticals that are legally available only with a physician's prescription. The second suit targets alleged spammers who sent unsolicited pitches via instant message, a relatively new form of spam the company called "spim."

Instant messaging, often known as IM, has grown in popularity for its ease of use, immediacy, and relative freedom from the onslaught of unwanted bulk messages that have been choking e-mail communication. AOL, which hosts the most widely used IM service, estimates that 1.5 billion instant messages move across its network every day.

AOL said it filed suit because it is beginning to see spammers target that large audience by sending e-mail either directly to IM users or to chat rooms they frequent.

AOL spokesman Nicholas J. Graham said the company each day takes action against more than 10,000 IM accounts that have been created or hijacked to spread spim. He said the number represents less than 1 percent of all accounts, which include AOL subscribers and others who use AOL's IM as a free, stand-alone service.

AOL is employing technology to block spim, including limiting how many instant messages can be sent from one account.

"Spammers are trying alternative weapons of mass annoyance," Graham said. "AOL is not going to be a safe haven" for IM spammers.

The suit does not name specific defendants, instead identifying 20 "John Does." In addition to sending sexually oriented and other marketing pitches, defendants are accused of visiting AOL's online chat rooms to gather IM account names and of fraudulently creating or stealing accounts.

AOL's legal action is part of an effort by some of the industry's biggest online providers to crack down on spam. Microsoft filed suit in Washington state, Earthlink filed suit in Atlanta, and Yahoo filed suit in California.

Yahoo's case, filed in the U.S. District Court in San Francisco, accuses East Coast Exotics Entertainment Group Inc., and Epoth LLC of disguising their identities, designing e-mail messages to get around its spam filters and using non-sexually explicit subject lines to conceal sexually explicit e-mails.

Epoth does not send "any kind of direct-marketing mail to anyone," said Steve Kupperman, the company's director of affiliate operations. He said Epoth operates several subscription-based adult Web sites and pays affiliates to direct viewers to those sites. East Coast Exotics, he said, is a defunct former affiliate.

If an affiliate uses spam, Epoth terminates its contract and refuses to pay for any services the affiliate provided, Kupperman said. He added that the company wants to work with Yahoo to resolve the matter.

Microsoft filed suit against three alleged spammers, two of whom it did not identify. Named were the New Jersey operators of a company called Herbal Technologies. In an interview, Steven Blaier said his company, which sells male sexual enhancement products, does not send spam, but that sometimes he runs into difficulties with affiliates that resell his products.

Blaier said he shuts down accounts whenever he gets complaints that one of his resellers is using spam. "We've been fighting spam," he said. "I'm a small business, I can't afford this."

Blaier added that he is getting out of the herbal supplement business, in any case.

"The market for herbal supplements is not as good as it used to be when we first got in it," he said, "now it's like everybody is doing it out of their garage."

Washingtonpost.com staff writer David McGuire and Washington Post staff writer Michael Musgrove contributed to this report.