Answer: a. use technical methods to gather preliminary information about the target
Step-by-step explanation:
Digital reconnaissance like its military equivalent is a way by which attackers monitor targets to gather information about security systems in place, potentially effective ways to attack the target and the benefits such as monetary gain or corporate advantage to be had by carrying out the attack.
Surveillance is not necessary to carry out malicious attacks, as in the case of the National Security Agency (NSA) which carries out reconnaissance missions to protect American citizens. (Although this is open to debate).
Surveillance techniques include hacking computer cameras.