Exam 212-82 topic 1 question 16 discussion

Tristan, a professional penetration tester, was recruited by an organization to test its network infrastructure. The organization wanted to understand its current security posture and its strength in defending against external threats. For this purpose, the organization did not provide any information about their IT infrastructure to Tristan. Thus, Tristan initiated zero-knowledge attacks, with no information or assistance from the organization.
Which of the following types of penetration testing has Tristan initiated in the above scenario?