Yes, FCI Danbury is a low-security federal prison, even after the transition to housing male inmates.
The facility is part of the Federal Bureau of Prisons and includes:
What that means:
So your brother going to Danbury will be entering a lower custody environment, not a high-security prison. Conditions are more structured than a camp, but far less restrictive than medium or high-security facilities.
It is considered one of the more manageable federal placements, especially for inmates with lower risk classifications.