Excel spreadsheets often contain sensitive information that needs to be protected. Setting passwords is a common way to restrict access, but sometimes those passwords are forgotten or need to be bypassed. This article explains techniques to crack or brute force Excel spreadsheet passwords.
Table of Contents
Understanding Excel Password Protection
There are two main types of password protection in Excel:
- Workbook (File) Protection – A password is set to open or modify the Excel file. This prevents unauthorized users from accessing the file.
- Worksheet Protection – Specific worksheets within the file are password protected. This allows selective access to sheets.
In both cases, the protection is based on a password hash stored in the file. Cracking involves attempting to determine the password that generates the hash.
Legal and Ethical Considerations
Before attempting to crack passwords, consider:
- You may be violating laws or terms of service by circumventing security.
- The file creator likely intended to restrict access for a reason.
- There may be confidential data exposed through unauthorized access.
Proceed carefully and only with authorization from the file owner.
Technique 1: Brute Force Attack
A brute force attack tries all possible password combinations:
- Specify a range of passwords to try – e.g. all combinations of lower/upper case letters and numbers up to 8 characters long.
- Software generates the password combinations.
- Each generated password is tested against the file.
- When the correct password is found, the file opens!
Pros: Works on any password if the search space is large enough.
Cons: Extremely slow on long/complex passwords.
Technique 2: Dictionary Attack
A dictionary attack tries passwords from a predefined list:
- Compile a password dictionary – common passwords, names, dictionary words, etc.
- Software tries each password in the dictionary against the protected file.
- Access is granted once a matching password is found.
Pros: Much faster than brute force for common passwords.
Cons: Fails on uncommon or random passwords.
Technique 3: Mask Attack
A mask attack tries passwords matching a specific pattern:
- Define a mask – e.g. 2 upper case letters + 4 digits.
- Software generates/tries passwords matching the mask.
- Testing continues until a match enables access.
Pros: Faster than brute force while allowing some complexity.
Cons: Requires guessing the right pattern.