Magnet Forensics is everything a start-up should be.

The company is lean, produce incredibly strong revenue growth and grows by retaining earnings, not seeking investment. But what makes it stand out is that the company’s technology offers a massive benefit to society.

Magnet, based in Waterloo, Ont., recovers deleted information from a computer. It’s used to help police find information that a suspect thought had been deleted. This could be communications between people, financial records, or even contraband photos. It’s particularly effective in the fight against child pornography.

“We’ve developed forensic software to recover internet-related communications from computers and mobile devises,” says CEO Adam Belsher. “Anything you’re doing on your computer to communicate—uploading pictures, going to chat rooms—there’s a good chance we can find it.”

I met Belsher last month when I was doing a story on the tech community in Kitchener-Waterloo for USA Today, and was amazed by the company. I usually only cover Atlantic Canadian companies, but here is a look at a Canadian company that can serve as a role model for others. And it started out as a free service.

The story began when a 26-year-old police officer called Jad Saliba contracted Hodgkin’s lymphoma and took a leave of absence to recover. When he returned, he was taken away from his beat work to become a digital forensics investigator and thrived at the position. He developed software that could recover deleted material from hard drives, and for two years gave it out free to other police forces.

In 2009, he left the police to launch the company, which was originally called JADsoftware. The company solved an extreme problem in the police department because it reduced the manual work needed in retrieving deleted files and greatly increased the amount of material that could be brought back.

Today, the company’s 1,500 clients include law enforcement agencies in almost 100 countries, such as the FBI and the office of Homeland Security in the U.S. The company’s revenues have increased 1,800% over the past two years and last year it captured the No. 16 spot on Profit magazine’s list of Canada’s fastest-growing companies. Belsher expects to improve on that position this year.

As it outgrows the police business, Magnet Forensics is looking for more corporate clients, and is already making headway in that market. When employees leave a company and sue for wrongful dismissal, they typically leave behind their desktop computers. Magnet’s technology can dig up material that can establish why the employee was let go and help to protect the employer.

Belsher, a former Research in Motion exec, joined the company in September 2011, and continued to grow the company. The company now has 30 employees and he expects to increase the work force in the coming year.

One interesting fact about the company is it has never raised equity investment, which means that it has preserved the founder’s capital and allowed the CEO to focus on the business rather than on fundraising.

Above all, Belsher and his colleagues thrive on knowing that they have helped fight the abuse of children. In the middle of our interview, the CEO whipped out his cell phone to read an email he had received the day before from a police officer in the U.S. who had just prosecuted a pedophile because of evidence retrieved with Magnet’s software. “If we can save just one kid’s life or stop the abuse of a child,” he says. “That’s what makes us tick, really.”