Microsoft has filed three more suits in its native Washington, against more of whom it calls the most egregious spammers. AOL sued in its home state of Virginia, Yahoo in California and EarthLink in Atlanta.

The suits, seven in total, variously allege violations of the federal CAN-SPAM Act, federal racketeering laws, as well as local state laws covering computer trespass, breach of contract and illegal spamming.

There’s quite a bit of cooperation behind the scenes, said Microsoft Internet safety enforcement attorney Aaron Kornblum. This is a unique area where our business interests are very closely aligned.

The defendants, mostly John Does who the companies intend to name through subpoena, are accused of sending spam advertising services as divers and porn, pharmaceuticals, insurance and mortgages.

Like previous bouts, the new lawsuits target primarily the bottom rungs of the spam ladder, the senders who get the commission rather than the companies that supply the services that are ultimately purchased.

There’s no intention to. These companies don’t necessarily pay attention to how these leads are generated, said EarthLink chief privacy officer Les Seagraves. What we have control over is what is actually hitting our network.

The companies reckon their suits are having an impact. Kornblum said 75 suits have been filed in the US by Microsoft. 10 to 15 of those have been resolved in one way or another, whether by default, bankruptcy, settlement or summary judgment.

One of AOL’s suits claims the defendant was spimming, or sending spam via instant messaging. Spimmers are essentially spammers who have been flummoxed by anti-spam efforts, AOL spokesperson Nicholas Graham said.

Spim is a new phenomenon, and comprises a very small percentage of instant messages AOL handles, Graham said. It’s also easier to block, as messages are all handled centrally by the IM company, but AOL wants wannabe spimmers to be afraid of lawsuits.

Our objective is to get in front of the J-curve, Graham said, referring to the speed at which email spam took off a few years ago, plotted on a graph. We’re trying to turn into an upside-down U.