Is it cyber-flirting or cyber-betrayal?

When Mayor Mary Anne Clancy of Newburyport, Mass., a married mother of three, engaged in a brief e-mail dalliance with a married gym teacher earlier this year, neither could have imagined the public embarrassment that would result from their private exchanges. But after Mrs. Clancy's husband, Brian, discovered the romantic e-mails this month, he allegedly assaulted Jason Beauparlant, the teacher, and was arrested. The ensuing headlines exposed the cyber-tryst.

The incident spotlights a largely hidden but rapidly growing phenomenon: cyber-affairs, romantic liaisons conducted via computer. Although a majority of such encounters never lead to a physical relationship - causing some observers to dub them "safe infidelity" - cyber-betrayals can seriously damage and even destroy the marriages of those involved, according to experts.

"It is a huge, huge issue," says David Greenfield, author of "Virtual Addiction." Noting that the Internet "has changed the whole landscape of human sexual behavior," he adds, "You've got this box on your desk that is accessible all the time with little or no effort. That just makes it too easy for a lot of people to communicate."

So easy, in fact, that they don't even need to leave home. "People sneak down to their computers while their spouse is sleeping and engage in these behaviors," Dr. Greenfield says. "They don't have to meet someone at the bar."

These cyber-flirtations are also attracting growing ranks of women. Although numbers are hard to pin down, researchers have found that "many more women than we ever imagined are using the Internet for sexually related activities," says Marlene Maheu, author of "Infidelity on the Internet."

In the past decade, lawyers have seen an increase in divorces and separations resulting from cyber-infidelity. "Some clients arrive at our office with hard drives they've yanked from their husband's computer, with downloaded e-mails, and with digital photos of their spouse's paramour," says Mark Guralnick, a divorce lawyer in Marlton, N.J.

In about 30 percent of cyber-affairs, Greenfield finds, the relationship escalates from e-mail to telephone calls to personal contact.

Even when no physical contact has occurred, these relationships can be "extraordinarily hurtful," says John Mayoue, a family law attorney in Atlanta. Unlike physical affairs, where a spouse doesn't know what a straying partner says during an illicit encounter, e-mail leaves a record.

"With a cyber-affair, I know every word that is communicated between the two persons," Mr. Mayoue explains. "They say things that are extraordinarily sexual, in ways that the husband and wife do not talk. They also appear to be speaking more from the heart than married folks speak to one another."

These cyber-romances raise new questions about what constitutes infidelity. In a statement to the press, Mrs. Clancy, the mayor, insisted that she did not have a physical relationship with Mr. Beauparlant. At the same time, she acknowledged that their online flirtation was "inappropriate" and expressed deep regret for the hurt she had caused her family. Her office did not return calls seeking comment.

What makes cyber-affairs deceptively easy and potentially confusing is the absence of visual cues that exist in face-to-face conversations, Dr. Maheu says.

She offers an example: "If two people are having lunch and one says something that is possibly flirtatious, the other person can respond by raising an eyebrow, looking away, dropping their jaw, or changing the subject. All those things could mean, 'I'm not going to flirt back.' "

Even if people do flirt over lunch, she says, "it typically takes many hours of flirting before anything sexual is mentioned, whereas in e-mail it could be in the next five minutes."

Without social cues as a guide, Maheu continues, people can find themselves exchanging steamy e-mails and then wondering the next morning how they could have said such things. They may write e-mail in a hurry, without considering their words.

Diane Daniels observed firsthand the devastation such relationships can cause. A friend who suspected her husband of cyber-cheating asked Ms. Daniels, a former technology expert in Norwich, Conn., to track his computer activity.

Daniels typed the husband's e-mail address into Google and found "tons of posts from him to other people," some bearing risqué titles.

When the wife confronted her husband, he admitted participating in chat rooms. "He didn't think it was wrong - it was just conversation," Daniels recalls.

The wife then e-mailed several women on his list, asking about their conversations with him. Some sent her copies of messages they had sent him or he had sent them. One woman was very embarrassed, Daniels says. "She would not have done it if she had known he was married."

Such deception about marital status is common in cyber-relationships, experts say. While an overwhelming majority of participants are in committed relationships, many claim they are available.

However devastated a wronged spouse may be by cyber-betrayal, Greenfield says that a large percentage of marriages rocked by cyber-affairs can be salvaged.

Maheu recommends marriage counseling. In her work with couples, she tells them, "Let's not overreact. Something has gone wrong. Let's address that. But let's not act as though this is a full-on, in-the-flesh affair."

That advice is often easier to accept in theory than in practice. For Daniels's friend, the months following her discovery of her husband's online trysts were difficult. "They have stayed together, and they continue to work on their marriage," says Daniels. "But she is very mistrustful of his Internet activity."

One of the first signs of cyber-affairs, Daniels notes, is a spouse who spends excessive time on the computer. Using multiple e-mail addresses could also serve as a warning of cyber-flirting.

"Ironically, the same tool that is used to conduct such an affair can be a means of discovering an affair," says Mayoue, the lawyer, who cautions that many cyber- dalliances, such as the one involving the Newburyport mayor, are eventually discovered. "While you are betraying your spouse with your computer, your spouse may be watching you with spyware."