PHNOM PENH, Cambodia — Microsoft and British intelligence specialists opened a two-week seminar Monday to train Cambodians how to fight against pedophiles who use the Internet to exploit children in the poor Southeast Asian nation.

About 150 Cambodian, Indonesian and Thai law enforcement officials and humanitarian workers will learn a range of computer know-how — from the basics of how the Internet works to tracing sex offenders to network security during the training, run by Britain’s National Criminal Intelligence Service, its National Crime Squad and software giant Microsoft.

“We recognize it is our responsibility to make cyberspace safe for all users, particularly children,’’ said Katharine Bostick, Microsoft’s senior director of legal and corporate affairs in Asia.

Cambodia has struggled to root out foreign pedophiles who target the country because of its lax law enforcement and deep poverty. Children often work in tourism locales, selling fruit, flowers or trinkets, leaving them vulnerable to pedophiles.

There are about 33,000 child sex workers in Cambodia, according to the U.N. children’s agency. In recent years, the country has experienced a sharp increase in the production and dissemination of child pornography via the Internet.

In June, the U.S. State Department listed Cambodia among 14 countries it deemed the worst at adequately addressing trafficking problems, including the trade of child sex workers.

“Many Cambodian children have never used a computer and they never in their lives used the Internet, but the abuse of Cambodian children by pedophiles occurs daily as pedophiles use the Internet and computers to plan, coordinate and facilitate their crimes against children,’’ Bostick said.

Cambodia is one of the world’s poorest countries, with the World Bank estimating about 42 percent of Cambodia’s 15 million people live on $1 a day or less. Many Cambodian police and prosecutors who attended Microsoft’s initial training course about computer-facilitated crime in July had never worked with a computer or the Internet, Bostick said.

But there are many Web sites with photos and information for pedophiles looking to commit crimes in countries such as Thailand and Cambodia.

“We are in a sense fighting fire with fire. Computer skills have been used to facilitate online abuse and computer skills can also be used to end it,’’ U.S. Ambassador Joseph Mussomeli said at the seminar opening.

“Cambodia is an attractive tourist destination with much to offer to visitors ... but it must be made a singularly unattractive destination for those wishing to prey on Cambodian children,’’ he later added.