Access Control Attacks
Gaining access (getting through that hard and crunchy outside) to a system or network is an attacker’s first objective. Attackers commonly use several methods of attack against access control systems, including
Brute-force or dictionary attack: The attacker attempts every possible combination of letters, numbers, and characters to crack a password, passphrase, or PIN. A dictionary attack is essentially a more focused type of brute force attack in which the attacker uses a predefined word list. You can find such word lists or dictionaries, including foreign language and special-interest dictionaries, widely available on the Internet for use in password-cracking utilities such as L0phtCrack and John the Ripper. Attackers typically run these password-cracking utilities against a copy of the target system’s (or network’s) security accounts database or password file. The utility creates hashes of passwords contained in its dictionary or word list, and then compares the resulting hash to the password file. These types of programs work very quickly and effectively (see the sidebar “How much brute force does it take to crack your passwords?” in this chapter), even when organizations use complex passwords, so the key to defending against a brute-force or dictionary attack is to protect your security accounts databases and password files.
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