There is a relatively new unit set up at a few federal prisons that you won't see in any prison movies. In fact, you won't read or hear about it much at all because it is very secretive. But word is starting to leak out about these units dubbed "Little Guantanamo."

They are called Communication Management Units, or CMUs. According to a 2009 report on an environmental Web site called Green in the New Red, these units were established in 2006 for prison officials to better monitor communication between certain inmates and the outside world.

According to a 2009 letter from convicted "eco-terrorist" Daniel McGowan, the Bureau of Prisons said:

The CMU is established to house inmates who, due to their current offense of conviction, offense conduct or other verified information, require increased monitoring of communication between inmates and persons in the community in order to protect the safety, security, and orderly operations of Bureau facilities and protect the public...The CMU is a self-contained general population housing unit.

Specifically, it was designed to capture talk between convicted terrorists and their possible confederates. Indeed, despite the Muslim population hovering at about 6% in the general U.S. prison population, McGowan's letter claimed the Muslim population inside his CMU at the Marion Federal Prison in Illinois is much closer to 65%-75%.

The ACLU is troubled that most of the inmates at CMUs are Muslim, raising concerns of racial profiling. It also said some of the prisoners are not serious security threats and should not be housed there.

McGowan said he was transferred there from a low-security facility in 2008 with a half an hour's notice and no explanation, which McGowan said is a violation of due process:

Since I got here, I have not had a hearing to contest the claims made in the “Notice to Inmate of Transfer to CMU,' some of which were woefully inaccurate.

The report from Green is the New Red said prison documents spell out the monitoring of prisoner communication. The site writes:

-- Phone calls: Only one phone call per week, limited to 15 minutes, live-monitored by staff and law enforcement (according to attorneys, this includes the NSA) and scheduled one and half weeks in advance. It must be conducted in English. Other prisoners get about 300 minutes a month.

-- Mail: All mail must be reviewed by staff prior to delivery to the inmate or processing at the post office. This means significant delays in communications (and, in my personal experience, letters frequently not being received by inmates).

-- Visits: Four hours of personal visits per month, non-contact, behind glass, and live-monitored by staff and law enforcement. It must be conducted in English. By comparison, at FCI Sandstone (where McGowan was previously housed) prisoners can receive 56 potential visiting hours per month. I have learned from attorneys and prisoners that when a CMU inmate is transferred to the visiting room, the entire facility goes on lock-down.

The government is not talking much about CMUs, and has not responded directly to any of these accusations.