For Lucy, 25, it all started just after Valentine's Day when she received a phone call claiming to be from the "Electronic Valentine's Service" with the message: "I've only got eyes for you."
At first she assumed it was a friend having a joke but, a few phone calls later, "it was blindingly obvious my friends knew nothing about it". The messages, intriguingly, were from a total stranger.
"It was very flattering," she admits. "And I did play along at the beginning. I was very excited about it. I even thought `God, it might be someone really nice'."
Before she knew it, Lucy's secret admirer had set up an anonymous e-mail address and tracked down her office e-mail address, and the messages started flying. The e-mails she received were laden with cryptic clues about who the man really was, and where he worked, and a flirty game of questions and answers soon took hold. Mr X, as he sometimes called himself, maintained that he was acting on behalf of someone else, and used a number of red- herring aliases to throw Lucy off his scent.
When she asked why he had decided to contact her, he said: "I was in a Valentine's Day mood, I was feeling frivolous. From what I'd seen, you appeared to be a bouncy, bubbly, smiley person, the type I'd like to know... contact was a challenge." He asked her what she wore "when alone in bed", and promptly sent her a baggy T-shirt.
He knew where she worked and where she went for lunch, but when the information he had on her became too personal she began to get worried. "He had found out my mother's name, and had watched me walk the dogs on the beach on my own. He knew the dogs' names, and had worked out where I lived. He had even been to the gym where I'm a member, as he said, `I saw you last night, and I like the blue swimming-costume'. It was getting creepy."
Some days Lucy would receive up to five or six e-mails, and if she didn't reply he would e-mail her: "Are you there? Anybody there?", and then "5", "4", "3", and so on, in an effort to get her to answer him.
"At this point I didn't know who he was, what he looked like, or if, when I went for lunch, he was behind me or not."
Given the clues that he had given her, Lucy managed to track down Mr X, who, it turned out, worked in an office opposite her own office window. And once she knew who he was she felt "frantic about knowing what he looked like" and determined to confront him.
"I sent him an e-mail saying `as soon as you get this why not call me'." And, sitting with her back to the window, she set up a number of mirrors so that she could tell who he was when he picked up the phone.
Having identified him, she confronted him in the lobby of his building. The person she met was a "shifty-looking" 50-year-old man, who wouldn't meet her eye, and still maintained he was the go-between acting on someone else's behalf. Lucy found the meeting very disturbing. In her lunch break she went to the police with all her evidence, and the next morning she received a bunch of flowers with the message: "It has been a good game, but now it's the end."
The e-mails have all but stopped, so Lucy has decided not to take further action, other than to keep her office blinds closed at all times.
Victim Support has had a lot of experience of stalker cases. "It is all to do with mind games and creating fear and mental intimidation," says a spokesperson. "It is intended to make the other person feel weak. The e-mail is just another tool to do that, and it is anonymous.
"With e-mails you never know how far or how close your tormentor is; they could be in the same office or across the country and, as the victim, you're just left waiting to see what's going to happen, and when."
Thanks to the Protection from Harassment Act, which came into force in June 1997, victims no longer have to endure harassment, as the act has made stalking by someone unknown to the victim a criminal act. Causing fear of violence carries a maximum penalty of five years in prison and/or an unlimited fine, while causing harassment carries the threat of six months in prison, and/or a pounds 5,000 fine.
However, a spokesman for Scotland Yard admitted that if the unwanted attention came from abroad, via the Internet for example, there would be little the law could do.
Patrick, 26, had to call in a lawyer when an innocent exchange over the Net went badly wrong. "My flatmate and I came back from the pub one night, we'd had a bit to drink and started playing on the Internet. We went into one of the chat rooms and met a young lady from Kentucky who said her husband beat her up."
Patrick left the room for five minutes and his friend gave the woman his address. Within days, Ralph Lauren shirts and long, hand-written, perfumed letters started arriving at his flat. "She said she was going to come to England to get married to me and have my children. At first it was quite funny. She also told me that she had inherited a farm in Kentucky, and was I going to move out to Kentucky with her?"
Patrick's admirer started sending photographs of herself with progressively fewer clothes on, until she was naked, and continued to tell him all about her life and her marriage problems. Over a six-month period he received 40 letters, which he never answered. "Then I got a letter saying she was divorcing the guy, and I was going to be named in a divorce case in Kentucky. I panicked at that point. I was really scared that she was going to turn up in London."
Patrick, who works in a bank, decided things had got out of hand and called in a lawyer to ask her to leave him alone. He received only one letter after that, saying, "I knew you would forget me". He has decided to steer clear of chat rooms in future.
Computer communication is, in the main, harmless, but its anonymity provides the perfect cover for those wanting to harass others and, in a sinister twist, people can and do disguise their addresses, or use other people's PCs to protect their identity further.
"You can be anything. You can pretend to be any sex, any age. You can lie about what you look like, or anything. It gives complete anonymity," says a spokesperson for Novell, a software company that has carried out research into spamming and cyber-stalking.
"It is important to keep your address to yourself. Don't give it to chat groups. Once it's on the Internet, you're open to spam, and open to cyber- stalking."
Debbie, 28, who works from home as a market researcher, regularly gave out her e-mail address on the Internet when she first went freelance, and made a lot of contacts. "One was very friendly and I thought, `I don't want to be rude', so I replied. He seemed okay at first, but became strange and obsessive."
If Debbie failed to give an immediate response to his messages, he would complain: "Why haven't you replied to my e-mail today? Where have you been?"
For the next six months, Debbie found herself bombarded with e-mails that became increasingly offensive and obscene. She tried to reason with her antagonist, but once he realised she was upset he simply stepped up his attack.
"The messages got personal, pornographic, and also violent, which was very intimidating."
The cyber-stalker used a number of PCs, or would mail her from a cyber- cafe to give the appearance, at first glance, of being a legitimate client. Generally, the messages took the form of old-fashioned dirty phone calls, with questions about her underwear and various obscene sexual propositions.
"If I had been working in an office, I could have gone home and left it behind; but my office is in my house, so it is very personal. You feel you've been violated, that they have got right into your house. It's as if they've got a direct line to you, and you can't help wondering if they somehow know your address."
In the end, Debbie hit back with a "very strongly worded e-mail", threatening to call in the police and "sue the pants" off her stalker, which seemed to do the trick.
"You have to remember," she points out with hindsight, "that there are a lot of weirdos out there; and with the Internet you get access to all of them, all over the world."