When Gerard Boniello, the managing partner at Omnium Protection Group, strolled through the New England Cannabis Convention last year as an attendee, recreational marijuana hadn't yet been legalized in Massachusetts and the medical marijuana program was still slowly getting off the ground.

But sensing an opportunity, Boniello returned to the convention this year, complete with a booth promoting his Waltham-based security firm.

"We're trying to be the go-to security company for the cannabis industry," Boniello said as crowds milled inside the Hynes Convention Center on a rainy Saturday.

Marijuana remains illegal under federal law and it's still a cash-based industry. And Boniello argues that puts pot shops, medical dispensaries and their delivery employees at risk.

"We want to fill that void," he said.

Having large amounts of cash on-site, not to mention high-value product, increases the likelihood of a robbery, Boniello said.

His 75-person firm offers a range of services, he said, including armed and unarmed guards or escorts, in uniform or in suits and ties.

"It depends on the facility and location," Boniello said.

His firm provided security for "American Hustle," which was partly filmed in Worcester and starred Christian Bale.

Omnium wasn't the only security firm at the Hynes Convention Center. American Alarm and Communications Inc., based in Arlington, Mass., had its own booth.

David Oles, an integrated systems consultant for American Alarm, said they put in fire alarm systems that detect smoke and heat, perimeter and interior motion sensors, entry and exit door controls, digital video surveillance and secure internet monitoring.

In business since 1971, the company got involved with the marijuana industry after Massachusetts voters legalized medical use in 2012.

"We saw an opportunity early on," Oles said.

The brochure at his table notes five out of six New England states have decriminalized marijuana, and now the substance is legal in Massachusetts and Maine.

"The security and life safety standards for marijuana growing facilities and dispensaries are not only strict, they are constantly evolving," the brochure says. "You need a security expert to keep your business in compliance with the law, and technology that won't harm your crops."

Massachusetts has 10 medical marijuana dispensaries, and retail pot shops aren't set to open until sometime in 2018.

The marijuana business remains a new industry. But based on the various vendors and crowds at the New England Cannabis Convention, it's already pulling companies toward branching out and offering services that they didn't think about a decade ago.

"It's a good place to go," Oles said.