In terms of computers, the set of ways in which an adversary can enter a system and can potentially cause damage is called:

The correct answer is A, Attack Surface. The attack surface of a system is the total collection of every point at which an unauthorised person could try to enter it or pull data out of it: open ports, running services, user accounts, login pages, removable drives and even the employees who can be tricked. Network administrators reduce risk by shrinking this surface, that is by closing unused ports and removing software that is not needed. Option B is wrong because an attack signature is the recognisable pattern of bytes or behaviour by which antivirus and intrusion detection software identify a known attack. Option C is wrong because an attack pattern is a general description of how a class of attacks is carried out, used while designing defences. Option D is wrong because an attack path, also called an attack vector chain, is the particular route a single intruder actually followed from entry to target, not the whole set of possible entry points.