Murdaugh, who is serving two life sentences after being convicted of murdering his wife and 22-year-old son, is behind bars at Kirkland Correctional Institution in Columbia, SC, where he's been placed in a single cell.

The SC Department of Corrections tells TMZ ... Murdaugh's infamy could put him at risk -- so, for the most part, he's being kept away from other inmates.

Murdaugh's single cell is made of concrete with a steel bed, toilet and sink. It's a stark contrast to the privileged lifestyle the disgraced powerhouse attorney once led.

We're told Murdaugh is under constant surveillance and he's not even eating with the other inmates. His meals are brought directly to his cell, where he eats alone -- that's how in peril prison officials feel he'd be in general population.

Murdaugh's only going to be at Kirkland for 45 days ... there's an evaluation period before he's assigned to a specific custody level, and new prison. At that point, we're told he will get his meals in the cafeteria with his fellow inmates, unless a specific threat is made against him.

For now, though, we're told Murdaugh is being escorted by at least one corrections officer whenever he leaves his cell ... and that's when he gets closest to other inmates, albeit for an extremely limited window.

As far as creature comforts, he can have a few. We're told he can buy a TV for his cell and pay for phone calls to family and friends.

So far, he hasn't been attacked or even threatened ... but Kirkland officials aren't taking any chances he gets harmed on their watch.