The correct answer is A.
OBJ-4.2: Since you scanned the system with the latest anti-virus signatures and did not find any signs of infection, it would most likely be evidence of a zero-day attack. A zero-day attack has a clear sign of compromise (the web tunnel being established to a known malicious server). The anti-virus doesn’t have a signature yet for this particular malware variant. Password spraying occurs when an attacker tries to log in to multiple different user accounts with the same compromised password credentials. Session hijacking is exploiting a valid computer session to gain unauthorized access to information or services in a computer system. Based on the scenario, it doesn’t appear to be session hijacking since the user would not normally attempt to connect to a malicious server. Directory traversal is an HTTP attack that allows attackers to access restricted directories and execute commands outside of the web server’s root directory. A directory traversal is usually indicated by a dot dot slash (../) in the URL being attempted.