1. A data transmission system for determining whether to allow transmission of data, the data transmission system comprising: a source for transmitting data destined for a destination over a network; a data acquisition means for acquiring a string of a predetermined length in bits (L) from the data; a complexity estimator for: (i) partitioning the acquired string into a partition of phrases, each of the phrases in the partition being unique and having one or more bits; (ii) determining a number of phrases (N) in the partition; and (iii) estimating a normalized complexity (C) for the Kolmogorov Complexity in the acquired string via 18 C &Congruent; N 2 &it; L ; a complexity evaluator for evaluating whether to allow transmission of the data based on a comparison of whether the normalized complexity estimate (C) is within a predetermined normal complexity estimate band; and the destination for receiving the data transmitted from the source based on the evaluation.