MS02 network null model is a random permutation of an original network (the observation). The MS02 null model preserves the number of linked partners for each node in the network, but randomly shuffles their partners.
Reference
1)Maslov S, Sneppen K. Specificity and stability in topology of protein networks.
Science. 2002, 296(5569):910-3.
2)Qin H, Lu HH, Wu WB, Li WH. Evolution of the yeast protein interaction network.
PNAS, 2003, 100(22):12820-4