She's only been with the Hamilton police child porn unit since January, but Leslie Lee already fielded about a dozen complaints about men trying to lure young girls over the Internet.

The sexual predators typically go into popular online chat or gaming rooms like Runescape to make their initial contact.

It's hard to know how widespread the problem is because parents are usually unaware and those who find out don't always go to police.

But Detective Constable Lee said potential signs include changes in a child's behaviour, like being sneaky about their Internet use or being tired in the morning, which may point to furtive late-night activity.

"I've had a couple cases where the parents interceded and then realized, 'We've failed here because she's back online talking to the guy,'" she said.

"They tend to prey on children that have low self-esteem as well, or maybe have issues socializing with other kids at school."

Det. Const. Lee offered a local glimpse into a global problem following this week's cyber-themed launch of Sexual Violence Awareness Month in Hamilton.

Noni Classen of the Canadian Centre for Child Protection said her Winnipeg-based non-profit group's cybertip.ca site has received 25,000 reports of online child sexual exploitation since 2004.

Ninety per cent deal with child pornography, she said, the vast majority involving kids under eight, nearly 40 per cent of whom are sexually assaulted. The other 10 per cent are reports of online luring, most of them targeting pubescent girls. Thirteen-year-olds are most at risk.

Predators typically start by posing as friends only interested in chatting and gradually introduce sexual elements into their conversations "to normalize sexual activity," she said.

Young girls whose computers have web cameras may be asked to do something that doesn't strike them as overtly sexual, like bending over to touch their toes, before requests move to more obvious activities - either online or in person.

"Because it's been so gradual, often they're desensitized to not seeing it as shocking, as they would if immediately they met them online and they said, 'Hey, can you take off your shirt,'" Ms. Classen said

"What offenders know is that it's easy to manipulate children. It's easy to dis-inhibit them and easy to confuse them."

Clare Freeman, chair of the Women Abuse Working Group, said online luring is just one aspect of sexual violence against teenage girls.

She noted, for example, that a Toronto safe schools study released in February revealed that a quarter of Grade 11 girls reported they were being sexually harassed at school.

As with workplace harassment and sexual assaults, such incidents are under-reported, Ms. Freeman said.

"It is very pervasive in a whole bunch of other areas of our daily life in Hamilton," she said.