An attacker has access to password hashes of a Windows 7 computer.

In the context of password hashes on a Windows 7 computer, a Rainbow Table attack is a feasible method an attacker might use to reveal passwords. This type of attack utilizes precomputed tables known as rainbow tables that contain hash values for every possible combination of characters. An attacker with access to password hashes can use these tables to look up the corresponding plaintext passwords. The effectiveness of rainbow tables stems from their ability to reverse cryptographic hash functions, which are used to store passwords securely. Since Windows 7 uses NTLM hashes, which are known to be vulnerable to rainbow table attacks, this method is particularly relevant12.

References: The explanation draws upon the known vulnerabilities of NTLM hash functions in Windows 7 and the general principles of rainbow table attacks as discussed in security literature12.