Remove the Password from a Zip File Without Knowing the Password

A password-protected ZIP file can be a pain to get through. You'll need specialized software to guess the password, and patience as your computer whirs through the task for the next several hours. Many sketchy websites take advantage of this frustration to spread viruses and adware with offers of "instant" or "free" password guessing. It's much safer to use a free trial of a respected program, and consider buying the full version if more features are needed.

Steps

  1. Know the risk. You'll need to download a program that can guess the password on the zip file. Before you do this, be aware that this can infect your computer with a virus. Review safe browsing practices and Protect-Your-Computer-With-Antivirus-Software before you continue.
    • The programs suggested below have been checked by several automatic malware scans, but this is not a guarantee of safety.
    • Most free trial versions will only crack short passwords. Be wary of free programs with no limitations — there is usually no incentive for a company to provide this, besides installing adware or other malware on your computer.
  2. Expect this to take time. In most cases, the program will take several hours to guess the password, unless the password is a single word. Passwords with 9 or more characters (and that don't spell a word) may take multiple days to guess.[1] There is no way to quickly guess the password within a few minutes.
    • The one exception is a ZIP archive that contains multiple files protected by the same password, one of which you already have access to. In this case, some programs can use a "known-plaintext" attack to figure out the password based on the file you have access to.[2]
  3. Download a cracker from Elcomsoft. Visit Elcomsoft.com to download the Advanced Archive Password Recovery program. Scroll to the bottom of the page, then click "Download free trial version." The trail version can only recover passwords 4 characters or shorter.[3] The full version costs $49.
    • If the ZIP file contains two or more files with different passwords, you'll need to create several copies and delete files within them, so that each ZIP archive only contains a single password.[1]
  4. Try ZIP Ultimate Cracker. You can download the shareware version here. This uses several good approaches, but the free version will only show you the first five characters. If this isn't enough to jog your memory, you may need to purchase the full version for $59, or purchase a single use for a smaller amount.[4]
    • This program has not been updated in a long time, so it may stop working after an update to your OS. It is made for Windows 2000, XP, Vista, and 7.
  5. Use Zip Password Recovery Professional. The trial version of this software is free, but will only crack passwords under a certain length. Visit this website and click Download Now to begin. Open the downloaded file to install the program.

Tips

  • There are a few different approaches a program can use. For best results, try one of each. These include:
    • Dictionary attack: Tests a list of words. Much faster than other options if it works, but high chance of failure as not all passwords fall in this category.
    • Brute force attack: Guesses every possible combination. Only works for short passwords and/or fast processors.
    • Brute force with mask: If you remember anything about the password, this will let you tell the program before it brute forces. For instance, it may only try combinations that use letters, not numbers.
  • After the file is extracted, the original ZIP archive will still be password-protected. To remove this protection, create a new ZIP archive of the extracted file by right-clicking and selecting "Send to" → "Compressed (Zip file)".[5]

Warnings

  • Copying/Downloading licensed software without paying for it, or without consent from the owner, is illegal in most countries. Password crackers can be used legally, but only to access files you have a right to access.
  • Brute force attacks can take a lot of time depending on your processor speed. If you do want to use this approach consider asking people with a better PC than yours to do it.

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Sources and Citations

  1. ↑ 1.0 1.1 https://www.elcomsoft.com/help/en/archpr/index.html
  2. ↑ https://www.elcomsoft.com/archpr.html
  3. ↑ https://www.elcomsoft.com/requirements.html?product=archprn
  4. ↑ http://www.vdgsoftware.com/uzc.html
  5. ↑ http://windows.microsoft.com/en-us/windows/compress-uncompress-files-zip-files#1TC=windows-7
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