New York — The Internet has helped many club companies attract new members and retain old ones with ease and convenience, via their own Web sites or through lead-generation sites. Elsewhere on the Web, however, lurks a growing number of scam artists who can damage a club's brand and reputation by advertising surprisingly cheap deals for memberships.

Over the past few months, several people bought what they thought were reduced-rate memberships to New York clubs operated by Equinox Fitness, New York Health & Racquet Club (NYHRC) and Town Sports International (TSI) by responding to an advertisement on Craigslist, only to find out later they were part of a scam.

A statement from Equinox says it does not allow or authorize anyone other than its own employees to sell memberships.

“The security of our members is very important to us, and we encourage people to be mindful when making an unauthorized purchase over the Web,” Equinox said. “In this situation, where we discovered the fraudulent purchase of memberships from Craigslist, we alerted the authorities and are fully cooperating with the investigation.”

J. Travis, brand manager for NYHRC, says the club has a list of about a dozen people who were victims of the online scam. NYHRC offered each of those victims a free six-month membership, and three of them accepted the offer, Travis says.

Memberships can be transferred from one person to another at NYHRC, but the transactions must be done through staff at the club, Travis says. He adds that the scam is a valuable lesson for prospective health club members.

“Do your homework,” Travis says. “If an offer is too good to be true, it probably is.”

New York Sports Club, operated by TSI, also had victims of the scam. The club allows the transfer of memberships, but like NYHRC, transfers must be handled at the club rather than by a third party.

“There are various ways to purchase a membership, including going into a club and buying directly from a membership consultant or purchasing a membership from our Web site,” a statement released by TSI said. “Additionally, if someone is interested in taking over an existing contract, we have a procedure for that as well.”

TSI adds that both parties need to come into a club to have the membership transferred and have the proper paperwork filled out by a New York Sports Club membership consultant.