A method and a system for transmitting confidential and non-confidential data blocks between intake units (1, 1′) and output units (3, 3′) of a communication system. The communication system has intake units (1) for confidential data blocks, intake units (1′) for non-confidential data blocks, output units (3) for confidential data blocks, and output units (3′) for non-confidential data blocks. A data distribution unit (2) transmits data blocks with confidential information from the intake units (1) for confidential information to the output units (3) for confidential information and data blocks with non-confidential information from the intake units (1′) for non-confidential information to the output units (3′) for non-confidential information. The two types of data blocks are differently marked, and the differently marked data blocks are transmitted in this form via the data distribution unit (2) in dependence on the marking from the intake unit in question to the corresponding associated output unit (3, 3′).