CYBER CRIME cost Australian's $4.8 billion last year. A computer expert demonstrates just how easily you could become a victim, and what you can do to prevent it. VISION: Thomas Aldahn

A CANADIAN teacher says his ex girlfriend has waged a vicious online hate campaign against him, posting allegations he's a psychopath and child molester.

Lee Ching Yan, 29, cyberstalked Lee David Clayworth, 35, for almost two-and-a-half years after the end of their brief relationship.

Mr Clayworth believes his ex is now living in Australia.

The two met while Mr Clayworth was teaching at an international school in Malaysia in 2010. After dating casually for several months, they broke up in December 2010.

Mr Clayworth told the Today show in the US that after the break-up Yan broke into his home, took his laptop, hard drive and other personal information.

"And then this online onslaught started," Mr Clayworth said.

"My email account was hacked into, my Skype account was hacked into. Emails started coming from my account ... claiming that I'm having sex with underage students."

"I did a Google search of my name and I saw profiles listed saying … I am a psychopath, I am a child molester, a paedophile, I am involved with my students and so on - and then that just steamrolled," he said.

Court documents show Yan retrieved nude photos of Mr Clayworth from his computer and posted them on several sites.

Mr Clayworth said anyone searching for his name online would immediately see the defamatory material.

CBC News reported he sued Yan in Malaysia, where the judge found her guilty of defamation and ordered her pay him the equivalent of $CA66,000 ($64,000) in damages. However, the harassment didn’t stop.

He was eventually granted a court order in Malaysia but Yan disregarded the court order and continued posting material online. She was eventually found in contempt of the court.

"She fled the country," Mr Clayworth said, and "things kept steamrolling on and on." He believes his ex is now in Australia.

Mr Clayworth has returned to Canada and has spent several months unsuccessfully looking for work. He believes potential employers are reading the false online material.

"It will never stop … it will go on and on. It’s been almost two-and-a-half years now," he said.

"This is a dark place. It’s a very, very dark place to be … and I am powerless."