8. An apparatus according to claim 1 , wherein condition (a) is satisfied.
8. An apparatus according to claim 1 , wherein condition (a) is satisfied. 15. An apparatus according to claim 8 , wherein said Javascript obtaining module is adapted to: leave unchanged in the Javascript in the HTTP response a function call to a random number function; and generate Javascript not originally present in the HTTP response that redefines the random number function so that the unchanged function call executes the generated Javascript, wherein the generated Javascript, when executed, uses the algorithm different from the first random number algorithm.