Why is /etc/shadow not world readable if the passwords are stored in an encrypted fashion?

Question

Options

• AThe encrypted passwords are still subject to brute force attacks.
• BThis is just for historical reasons.
• CThere is other information in the file that needs to be kept secret.
• DThe passwords can be decrypted by anyone with root access.

• A
  74% (14)
• B
  5% (1)
• C
  11% (2)
• D
  11% (2)

Explanation

Even though passwords in /etc/shadow are hashed (not encrypted), hashing is a one-way transformation - not decryption protection. If the file were world-readable, any user could copy the hashes and run brute force or dictionary attacks offline, systematically guessing passwords until a match is found. This is why A is correct: the hashing algorithm doesn't protect against an attacker who has unlimited time to guess.

Why the distractors are wrong:

• B is wrong because the restriction isn't merely historical - it's an active, deliberate security control still critical today.
• C is partially true (the file does contain aging/expiry metadata), but that's not the primary reason for the restriction; the real concern is password crackability.
• D is wrong because root access legitimately allows reading the file - that's not a vulnerability, it's expected behavior; the threat is unprivileged users gaining access.

Memory tip: Think of a hash like a fingerprint - you can't reverse it, but if an attacker collects your fingerprint, they can compare it against a database of millions until they find a match. Hiding the file is like not leaving your fingerprints everywhere.

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