A security unit (34, 34') for an industrial control system, comprising: an interface adapted to communicate with a plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) of an industrial control system via a data network; a security assignor adapted to access a first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) among said plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) via said interface, and adapted to assign a first security level pertaining to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); said security assignor further adapted to access a second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) among said plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) via said interface, and to assign a second security level pertaining to said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) to said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), wherein said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) is different from said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); wherein said security assignor is adapted to assign said first security level and said second security level to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) and second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), respectively, in accordance with a system security level pertaining to said industrial control system; wherein said second security level is equal to said first security level; wherein said security assignor is adapted to receive a message from said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) indicating that said first security level has been adopted by said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), or cannot be adopted by said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); and/or wherein said security assignor is adapted to receive a message from said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) indicating that said second security level has been adopted by said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), or cannot be adopted by said second component (14 1 - 14 6, 16 1 -16 12, 20, 24, 26, 30, 32, 40, 42, 44). an interface adapted to communicate with a plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) of an industrial control system via a data network; a security assignor adapted to access a first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) among said plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) via said interface, and adapted to assign a first security level pertaining to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); said security assignor further adapted to access a second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) among said plurality of components (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) via said interface, and to assign a second security level pertaining to said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) to said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), wherein said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) is different from said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); wherein said security assignor is adapted to assign said first security level and said second security level to said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) and second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), respectively, in accordance with a system security level pertaining to said industrial control system; wherein said second security level is equal to said first security level; wherein said security assignor is adapted to receive a message from said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) indicating that said first security level has been adopted by said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), or cannot be adopted by said first component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44); and/or wherein said security assignor is adapted to receive a message from said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44) indicating that said second security level has been adopted by said second component (14 1 - 14 6, 16 1 - 16 12, 20, 24, 26, 30, 32, 40, 42, 44), or cannot be adopted by said second component (14 1 - 14 6, 16 1 -16 12, 20, 24, 26, 30, 32, 40, 42, 44).