When Alisha Karen ended her marriage she knew her husband wouldn't let her go quietly. "He had been abusive," she says, "so I expected him to punish me for leaving."
She was right. Last November, a local court heard evidence of a two-year campaign of harassment Thomas Welsh had directed at Alisha since their split. Immediately after ending their relationship, she had been bombarded with sexually explicit text messages and photographs on her mobile phone. Worse was to come.
She soon discovered that her details had been posted on a website aimed at cross-dressers and sado-masochists, where she had been advertised as being "available for sexual services". "It was horrific," she says. "I was getting all these disgusting emails and phone calls."
Cyber-stalking - the use of technology such as the internet and mobile phone - to track victims has increased sharply in the past few years. Many of the offenders are men who are disgruntled and angry at being rejected by their partners. Rather than creeping around outside the victim's home, or following her to work, though, some of these men, as Allison found, post details of their victim on websites containing sexually explicit material.
Others email pornographic photographs and videos of the victim (often taken without her knowledge or consent) to family members and work colleagues.
Cyber-stalkers sign their victims up directly to public sites where people advertise for casual sex, often writing their victim's profile as if she is available for all manner of sexual activity with strangers.

Info from personal blog
Such men, according to Hamish Brown, a former police officer and an expert on stalking and harassment, fit the profile of the "obsessional stalker" - an ex-partner who refuses to believe that a relationship is over. "These men refuse to give up, however clearly the victim tells him she doesn't want to know. He has this attitude of, 'If I can't have her, no one will.”
When Sophie Green started getting emails from her ex-partner, Simon Ward, saying things such as, "Oh, you saw so-and-so and went to that bar at that time, did you?", she realised he was tracking her movements through information she had written on her personal blog.
According to research by an expert on stalking, Dr Lorraine Sheridan of Leicester University, half of all victims are now harassed via the internet. And despite the image of the stalker as a creepy loner, there is a growing online community to help and support the cyber-stalker's efforts. So-called "revenge" websites, such as Avengers Den and Get Revenge on Your Ex, are becoming more popular, says Sheridan.
I spent an hour surfing such sites and what I found was disturbing. One site advertised itself as being able to assist those wishing to experience "the pure, unadulterated satisfaction you get from totally crushing your ex's self-esteem and annihilating their reputation".
The majority of those leaving posts seem to be men though there are no gender stats.
"Whether the stalker harasses his victim by letter, in person or by email is irrelevant," says Brown. "But victims of cyber-stalking have often told me they get terrified of the 'invisible' stalker who is hiding in cyberspace, because he could be anyone and everywhere."
The good news is that cyber-stalkers are more likely to be caught than others, because there is usually a trail of evidence from computers and mobile phones. However, stalkers are usually determined, and often put time and effort into becoming technical experts.
The effects on victims of stalking do not go away when the stalker finally does. "It will take me years to get over what he did and to feel safe again," says Alisha. "I just wish something had been done to stop him before he almost ruined my life."
Some names have been changed.
The Guardian