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Capec-16 Detail

Dictionary-based Password Attack

Detailed Software Likelihood: Medium Typical Severity: High

Parents: 49

Threats: T71 T263 T271 T279 T292 T307 T385 T398

Tools: 19

Description

An attacker tries each of the words in a dictionary as passwords to gain access to the system via some user's account. If the password chosen by the user was a word within the dictionary, this attack will be successful (in the absence of other mitigations). This is a specific instance of the password brute forcing attack pattern. Dictionary Attacks differ from similar attacks such as Password Spraying (CAPEC-565) and Credential Stuffing (CAPEC-600), since they leverage unknown username/password combinations and don't care about inducing account lockouts.

Not present

Explore

  1. Determine application's/system's password policy: Determine the password policies of the target application/system.

    2. Techniques
    Determine minimum and maximum allowed password lengths.
    Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc., or whether they are allowed to contain words from the dictionary).
    Determine account lockout policy (a strict account lockout policy will prevent brute force attacks).

  2. Select dictionaries: Pick the dictionaries to be used in the attack (e.g. different languages, specific terminology, etc.)

    3. Techniques
    Select dictionary based on particular users' preferred languages.
    Select dictionary based on the application/system's supported languages.

  3. Determine username(s) to target: Determine username(s) whose passwords to crack.

    4. Techniques
    Obtain username(s) by sniffing network packets.
    Obtain username(s) by querying application/system (e.g. if upon a failed login attempt, the system indicates whether the entered username was valid or not)
    Obtain usernames from filesystem (e.g. list of directories in C:\Documents and Settings\ in Windows, and list in /etc/passwd in UNIX-like systems)
Exploit

  1. Use dictionary to crack passwords.: Use a password cracking tool that will leverage the dictionary to feed passwords to the system and see if they work.

    2. Techniques
    Try all words in the dictionary, as well as common misspellings of the words as passwords for the chosen username(s).
    Try common combinations of words in the dictionary, as well as common misspellings of the combinations as passwords for the chosen username(s).
  1. The system uses one factor password based authentication.
  2. The system does not have a sound password policy that is being enforced.
  3. The system does not implement an effective password throttling mechanism.
  1. A machine with sufficient resources for the job (e.g. CPU, RAM, HD). Applicable dictionaries are required. Also a password cracking tool or a custom script that leverages the dictionary database to launch the attack.
Low
A variety of password cracking tools and dictionaries are available to launch this type of an attack.
Integrity Access Control Authentication Confidentiality
Modify Data Gain Privileges Gain Privileges Gain Privileges
Read Data
  1. A system user selects the word "treacherous" as their passwords believing that it would be very difficult to guess. The password-based dictionary attack is used to crack this password and gain access to the account.
  2. The Cisco LEAP challenge/response authentication mechanism uses passwords in a way that is susceptible to dictionary attacks, which makes it easier for remote attackers to gain privileges via brute force password guessing attacks. Cisco LEAP is a mutual authentication algorithm that supports dynamic derivation of session keys. With Cisco LEAP, mutual authentication relies on a shared secret, the user's logon password (which is known by the client and the network), and is used to respond to challenges between the user and the Remote Authentication Dial-In User Service (RADIUS) server. Methods exist for someone to write a tool to launch an offline dictionary attack on password-based authentications that leverage Microsoft MS-CHAP, such as Cisco LEAP. The tool leverages large password lists to efficiently launch offline dictionary attacks against LEAP user accounts, collected through passive sniffing or active techniques.See also: CVE-2003-1096

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