The announcement came alongside other announcements by state and federal authorities in the Northeastern US that they are undertaking efforts to cut down on deceptive spamming and other illegal behavior on the Internet.

While the FTC has coordinated similar efforts in the Midwest and Pacific Northwest earlier this year, combating spam is a difficult business because, though it is a nuisance, the practice is not illegal under US law. All of those facing FTC lawsuits this week are charged with violating existing laws against deceptive and unfair trade practices.

One defendant used the logos of well-known financial institutions to collect personal financial information from respondents. Another sent messages advertising a service that promised to eliminate spam. The product, sold by NetSource One, actually attracted more spam, according to the FTC. Four others were charged with sending illegal chain letters asking for money. The defendents agreed to stop or face fines.

The FTC said another 100 pyramid scheme operators received warning letters from authorities. And FTC investigators have placed special e-mail addresses around the Internet to see if spammers will pick them up.