In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
the many existing cyber warfare scenarios, not excluding a coordinated cyber attack that sabotage multiple infrastructure assets, erecting proper defences is . Anonymity and low cost have meant that small disaffected groups — apart from hostile states and official agencies — could to cyber techniques.
erecting proper defences is .