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.
Likelihood Of Attack
The table below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Standard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.
Determine application's/system's password policy: Determine the password policies of the target application/system.
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).
Select dictionaries: Pick the dictionaries to be used in the attack (e.g. different languages, specific terminology, etc.)
Select dictionary based on particular users' preferred languages.
Select dictionary based on the application/system's supported languages.
Determine username(s) to target: Determine username(s) whose passwords to crack.
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)
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.
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).
The system uses one factor password based authentication.
The system does not have a sound password policy that is being enforced.
The system does not implement an effective password throttling mechanism.
A variety of password cracking tools and dictionaries are available to launch this type of an attack.
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.
Many invalid login attempts are coming from the same machine (same IP address) or for the same log in name. The login attempts use passwords that are dictionary words.
The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Create a strong password policy and ensure that your system enforces this policy.
Implement an intelligent password throttling mechanism. Care must be taken to assure that these mechanisms do not excessively enable account lockout attacks such as CAPEC-02.
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.
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
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.