People stuff them in footballs and toss them over barbed wire fences into prison yards. They're smuggled in by prison visitors or correctional officers who sell them for hundreds of dollars behind bars.
However the cell phones get in, Jeffrey Callison with the California Department of Corrections and Rehabilitation (CDCR) said contraband cell phones in California prisons are a growing problem.
"The number of contraband cell phones confiscated has risen each year, almost exponentially to 15,000 just last year in California," Callison said.
And that's created some high-profile problems.
Inmates have been found to be keeping Facebook pages, an inmate in South Carolina called a hit on a correctional officer from prison, and Charles Manson, kept inside one of the most secure cells in California, has been caught with cell phones twice.
Which is why the state rolled out a high-tech approach Monday that they hope will at least minimize the use of illegal phones, starting with Avenal State Prison in the Central Valley.
The approach, called "managed access" creates an umbrella over the prison, blocking cellular transmission from all but pre-authorized phones.
Global Tel Link, the same company that operates the state prisons' payphones is paying for the technology in the hopes that they will recapture inmate customers who've increasingly turned to contraband cell phones to keep in touch with the outside world.
But not everyone is happy about the approach.
In May, the nonpartisan California Council on Science and Technology released a report on managed access at the request of several lawmakers. The report raised concerns about the efficacy of the technology, including the fact that it doesn't block 4G or satellite transmissions.
The report also pointed out that the technology didn’t work well when a Mississippi prison tried it out.
Instead, the reports authors recommended that California, like many other states and the federal prison system, screen correctional officers for contraband before they start their shifts. The California Correctional Peace Officers Association has said that kind of screening would violate correctional officers’ contracts.
Callison said CDCR is aware that no one approach to combating contraband is flawless, and that managed access is a free-to-taxpayers technique that will supplement other methods, like phone-sniffing dogs and higher penalties for those caught with phones.