PS 5100.08, Chapter 4
Classification is necessary to place each inmate in the most appropriate security level institution that also meets his/her program needs and is consistent with the Bureau’s mission to protect society.
BOP facilities are classified into Minimum, Low, Medium, High, and Administrative facilities based upon the level of security and staff supervision the institution is able to provide.
Initial security designation data is entered into SENTRY* based upon information contained within the PSR.
*SENTRY is a real-time information system consisting of various applications for processing sensitive but unclassified (SBU) inmate information and for property.
Source: Inmate Security Designation and Custody Classification