Multiple choice technology security

Why is “Black List” input validation considered a weak validation method ?

  1. Because the validation settings are hard coded.

  2. Susceptible to bypass using various forms of character encoding

  3. Because it's difficult to implement a black list filter that also takes into account data sent using the POST method

  4. Because it is typically implemented using regular expressions to match known good data patterns
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Blacklist validation is weak because attackers can easily bypass it using various character encoding techniques like URL encoding, Unicode variations, or hex encoding. Since blacklists try to block specific bad patterns, they inevitably miss novel attack vectors. Whitelist validation (allowing only known good patterns) is much more secure.

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