Someone is always watching when you’re behind bars.

Corrections officers are tasked with keeping an eye on inmates in jails and prisons around the clock. Whether they’re eating, sleeping or enjoying the limited recreational time they have, an officer is always close by. Even collect phone calls are closely monitored.

But since the rise of mobile communications, inmates have found at least one way to take back a bit of the privacy they were forced to give up — by smuggling in cell phones.

“I think (cell phones) are the biggest threat to every staff member’s safety, as well as inmates inside and members of the public,” Council of Prison Locals National President Eric Young told the University of Maryland’s Capital News Service. “We don’t agree with inmates having cell phones.”

Virtually all avenues of communication available to inmates are subject to supervision, and the ability to get cell phones into prisons and jails offers a means of communication and coordination that is nearly impossible for corrections officers to control.

There is no shortage of ways inmates can gain access to cellphones, and they frequently get creative.

“We’ve had footballs — literal footballs — from individuals outside of the prison who throw them over the gate, and on the inside of the football there is a (cell phone glued down),” Young said.

Once in possession of a cell phone, an inmate can network with people outside the prison to move illegal contraband. They’ve also been used for intimidation and carrying out homicides.

“We had a lieutenant that was killed as a result of busting open a cell phone smuggling ring inside of a (detention center) in Puerto Rico,” Young said, referring to Lt. Osvaldo Albarati, who was fatally shot in 2013. “He was actually one of the key investigators working inside our prisons . that busted open the smuggling ring. The inmates were very despondent about it.”

“So from inside the prison, prisoners used cell phones to coordinate with people outside the prison to follow him, and they shot and killed him.”

Albarati is also the namesake of federal legislation, the “Lieutenant Osvaldo Albarati Correctional Officer Self-Protection Act of 2017,” which would give correctional officers more access to personal firearms to defend themselves. The U.S. House Judiciary Committee approved the measure on Thursday.

So with smuggled cell phones presenting a clear danger, how do jails and prisons put a stop to it? It’s a daunting task, made no less challenging by the fact that technology known as “cell jamming,” which effectively disrupts mobile communications inside a rough perimeter, is banned by the Federal Communications Commission.

“Jammers are more than just a nuisance; they pose an unacceptable risk to public safety by potentially preventing the transmission of emergency communications,” according to a report on the FCC’s website, which points out that jammers block signals indiscriminately.

“We are working with our agency to develop other initiatives inside of our prisons that block cell phone signals out of our prison,” Young said. “And I’m hoping some form of technology like that will be rolled out in the future that’ll not only protect the good order inside of our prison but also keep our communities and our staff safe.”

Across the country, technology firms are answering that call, developing ways to block mobile signals inside prison walls.

Hanover, Maryland-based Tecore Networks developed the Intelligent Access Controller Managed Access system, for instance, which is used to intercept cellphone signals in Baltimore’s Metropolitan Transition Center and Baltimore City Detention Center.

The system works by creating a “radio frequency umbrella around a precisely defined target area,” according to Tecore’s website. Communications from mobile devices within the area are intercepted, but the system allows communication from pre-authorized sources, including calls to 911.

“At one facility (our system) captured more than 10,600 calls and messages in its first 24 hours of operation,” Tecore CEO and Founder Jay Salkini says. “That number dropped to less than 4,000 attempts per day by the end of that first month.”

Twenty-two different forms of technology are accounted for by the system, according to Salkini.

“Officers and jail employees are safer knowing that they and their families are not being targeted by inmates,” Salkini said. “Before, inmates were able to capture images, send videos and coordinate hits or shake-up on personnel.”

Tecore’s system operates within FCC standards and does not interfere with devices near the prison, which is a common issue among cell jamming methods.

However, The Baltimore Sun reported in 2014 that people travelling near the Baltimore City Detention Center claimed their cell phone signals were interrupted, but Tecore says they haven’t received any complaints about the system affecting people outside the prison walls.

Earlier this month, the state of Maryland approved a $972,400 contract extension with the company through April 2019. Salkini said that the money is put toward maintaining and monitoring their system 24/7. Tecore has been contracted by the state of Maryland since 2013.