Four of the largest internet providers in the US announced they have filed six lawsuits against hundreds of spammers.
People are bombarded with spam in computer inboxes
Microsoft, AOL, Earthlink and Yahoo are joining forces to fight the millions of junk e-mails sent out every day.
The companies said the defendants include some of the nation's "biggest" and "baddest" large-scale spammers.
The actions are believed to be the first major industry lawsuits under new anti-spam legislation passed in the US earlier this year.
"We're trying to hit the biggest, the baddest, the most notorious spammers," said Randall Boe, AOL's top lawyer. "The next step will be to put them out of business."
The four providers have shared information and resources in an effort to clamp down on the menace of spam.
They are helped in large part by new US legislation passed at the beginning of the year that addresses some of the tricks spam gangs use to get their unwanted messages to millions of internet users.
The law, called the CAN_SPAM Act, demands that unsolicited e-mails must include a mechanism for recipients to indicate that they do not want future mass mailings.
It also prohibits spammers from disguising their identity by using a false return address or misleading subject line. It also aims to halt the practice of harvesting addresses from web sites.
"Congress gave us the necessary tools to pursue spammers with stiff penalties, and we in the industry didn't waste a moment moving with speed and resolve to take advantage of the new law," said Mr Boe.
The BBC's Kevin Anderson in Washington says that by some estimates more than 60% of e-mail travelling over the internet now is spam.
According to anti-spam activists Spamhaus, 90% of junk e-mails can be traced to just 200 known spam gangs.
In-boxes around the world are full of unwanted e-mails offering weight loss supplements, hair growth products and links to pornography.
It is estimated that more than half of the world's email traffic is spam
Some experts argue that the new law will do little to curb spam and leaves enough loopholes for spammers to keep operating from other countries.
But Microsoft's lawyer, Nancy Anderson, said she believes the new law will help because "most of the individuals involved in spam reside in the US".
"Just putting a computer offshore doesn't put them out of reach," she said.
The firms have filed separate legal complaints in courts in California, Georgia, Virginia and Washington against six operations said to be responsible for millions of spam emails.
The lawsuits in some cases name "John Doe" or unknown defendants, although the firms say the identities are likely to be obtained through the court.
AOL is suing Davis Wolfgang Hawke of Massachusetts, said to be also known as Dave Bridger, and Braden Bournival of New Hampshire for sending millions of spam messages.
Microsoft is suing Florida-based JDO Media for what it says is the company's "multi-level marketing program using fake identities and misleading subject lines such as 'This Is Your Lucky Day...'".
The provider is also suing the so-called Super Viagra Group routing its e-mail messages through hijacked computers around the world.
Yahoo's lawsuit names a Canadian-based firm - and operators Eric Head, Matthew Head and Barry Head - it claims is responsible for millions of spam e-mail messages to Yahoo users.