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CAPEC-55: Rainbow Table Password Cracking

Rainbow Table Password Cracking
Definition in a New Window Definition in a New Window
Attack Pattern ID: 55
Abstraction: Standard
Status: Draft
Completeness: Complete
Presentation Filter:
+ Summary

An attacker gets access to the database table where hashes of passwords are stored. He then uses a rainbow table of pre-computed hash chains to attempt to look up the original password. Once the original password corresponding to the hash is obtained, the attacker uses the original password to gain access to the system.

A password rainbow table stores hash chains for various passwords. A password chain is computed, starting from the original password, P, via a reduce(compression) function R and a hash function H. A recurrence relation exists where Xi+1 = R(H(Xi)), X0 = P. Then the hash chain of length n for the original password P can be formed: X1, X2, X3, ... , Xn-2, Xn-1, Xn, H(Xn). P and H(Xn) are then stored together in the rainbow table.

Constructing the rainbow tables takes a very long time and is computationally expensive. A separate table needs to be constructed for the various hash algorithms (e.g. SHA1, MD5, etc.). However, once a rainbow table is computed, it can be very effective in cracking the passwords that have been hashed without the use of salt.

+ Attack Steps
  1. 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.).

    Determine account lockout policy (a strict account lockout policy will prevent brute force attacks).

  2. Obtain password hashes: An attacker gets access to the database table storing hashes of passwords or potentially just discovers a hash of an individual password.

    Obtain copy of database table or flat file containing password hashes (by breaking access controls, using SQL Injection, etc.)

    Obtain password hashes from platform-specific storage locations (e.g. Windows registry)

    Sniff network packets containing password hashes.

  1. Run rainbow table-based password cracking tool: An attacker finds or writes a password cracking tool that uses a previously computed rainbow table for the right hashing algorithm. It helps if the attacker knows what hashing algorithm was used by the password system.

    Run rainbow table-based password cracking tool such as Ophcrack or RainbowCrack. Reduction function must depend on application's/system's password policy.

+ Attack Prerequisites
  • Hash of the original password is available to the attacker. For a better chance of success, an attacker should have more than one hash of the original password, and ideally the whole table.

  • Salt was not used to create the hash of the original password. Otherwise the rainbow tables have to be re-computed, which is very expensive and will make the attack effectively infeasible (especially if salt was added in iterations).

  • The system uses one factor password based authentication.

+ Typical Severity


+ Typical Likelihood of Exploit

Likelihood: Medium

+ Methods of Attack
  • Brute Force
+ Examples-Instances


BusyBox 1.1.1 does not use a salt when generating passwords, which makes it easier for local users to guess passwords from a stolen password file using techniques such as rainbow tables.

Related Vulnerabilities

+ Attacker Skills or Knowledge Required

Skill or Knowledge Level: Low

A variety of password cracking tools are available that can leverage a rainbow table. The more difficult part is to obtain the password hash(es) in the first place.

+ Resources Required

Rainbow table of password hash chains with the right algorithm used. A password cracking tool that leverages this rainbow table will also be required. Hash(es) of the password is required.

+ Indicators-Warnings of Attack

This is a completely offline attack that an attacker can perform at their leisure after the password hashes are obtained.

+ Solutions and Mitigations

Use salt when computing password hashes. That is, concatenate the salt (random bits) with the original password prior to hashing it.

+ Attack Motivation-Consequences
ScopeTechnical ImpactNote
Gain privileges / assume identity
+ Purposes
  • Penetration
+ CIA Impact
Confidentiality Impact: HighIntegrity Impact: HighAvailability Impact: Low
+ Technical Context
Architectural Paradigms
+ Content History
CAPEC Content TeamThe MITRE Corporation2014-06-23Internal_CAPEC_Team

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Page Last Updated or Reviewed: August 04, 2017