Comprehensive and Detailed Explanation:

The attacker’s goal is to create an account entry in /etc/passwd that grants root privileges. In Unix/Linux, the UID and GID determine privileges; UID 0 is the root account. The line the tester appended sets UID/GID to 1001:1001, which does not grant root privileges. Changing those numeric fields to 0:0 (UID 0, GID 0) will cause the new account to be treated as root when the entry is parsed by the system, enabling a root-level login with the supplied hash.

Additional correctness notes (non-exploitating guidance):

The appended line must match the exact /etc/passwd format (no stray spaces or malformed punctuation).

The password hash must match the system’s expected scheme; openssl passwd produced an MD5-style hash ($1$...) — ensure the hash is correctly copied (case/character fidelity matters).

Modifying /etc/passwd in this way is destructive and illegal without explicit authorization; in an authorized testing engagement, these details are taught to illustrate how misconfigurations lead to privilege escalation.

Why other choices are incorrect:

A: The redirect >> /etc/passwd (append) is appropriate for adding a line; switching to a single redirect is not the central issue.

B: md5sum would produce a raw MD5 digest, not the salted hash format expected by /etc/shadow//etc/passwd entries.

C: Logging in via SSH does not enable the exploit; creating the user with UID 0 is the required change.

CompTIA PT0-003 Mapping:

Domain 3.0 Attacks and Exploits — local privilege escalation techniques and understanding of OS account mechanics.

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