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71 votes
Accepted

How do unzip programs check if the password is correct?

Thinking of it as "password protection" slightly misrepresents the actual situation. What happens when you password-protect a zip file is that the archive is encrypted using a symmetric algorithm (...
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  • 2,485
37 votes

How do unzip programs check if the password is correct?

It depends on the specific zip crypto algorithm. For example, the original ZIP specification used the password to initialize a set of three 32-bit decryption keys. Then the ZIP header (12 random ...
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  • 4,810
26 votes
Accepted

Crack 7Z password if I also have the original file

7z uses AES-256 with the CBC mode of operation for encryption. Since AES in CBC mode is resistant to known-plaintext attacks ( The CBC mode has greater security than KPA, it has Ind-CPA), having the ...
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  • 10.8k
25 votes
Accepted

How is malware distributed within zip files?

Do you remember "I love you" ? Human curiosity often does the trick, unarchiving the zip and then executing the JS (via the windows scripting host that does not follow the same restrictions as a ...
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  • 14.3k
25 votes
Accepted

At which point can a system be compromised when downloading archived data from an untrusted source?

1 should not present any danger as long as the file is just saved somewhere and no attempts to open it with anything are made. If you view it even with a text editor, there's already a small danger of ...
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  • 8,799
24 votes
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Is it possible to read a text file inside a password-protected zip file without the password?

No. There are two ways of zip encryption, a classic one, which is weaker, and a newer one based on AES. In both cases the password is needed in order to decrypt the contents (i.e. it's not just UI, ...
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  • 17.4k
22 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

Yes. The zip or rar file will be encrypted like all other files so that they are useless for you. The only protection is making backups to another physical storage. This will help independantly of ...
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  • 2,614
18 votes
Accepted

How zip symlink works?

Symlinks are like shortcuts, so if you create a symlink pointing to /etc/passwd, when you open the symlink your O.S. will open /etc/passwd. How the attack works? 1) Create a symlink in your computer ...
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  • 1,316
18 votes

How to recover a lost zip file password?

You can also use this shell script. Source: http://synacl.wordpress.com/2012/08/18/decrypting-a-zip-using-john-the-ripper/ #!/bin/bash echo "ZIP-JTR Decrypt Script"; if [ $# -ne 2 ] then echo "Usage ...
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  • 511
18 votes
Accepted

Is it safe to click on zip or rar file?

A well known trick will be to disguise a PE or Executable program into an another file, a PDF or an archive for example. Since most of people rely on the file's icon or extention, it works pretty ...
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  • 1,625
16 votes
Accepted

What encryption method is used by the zip program in macOS?

It's using the original PKZIP 2.0 encryption (variously referred to as "traditional" or "legacy" encryption), described in section 6 of the .ZIP file format specification. It's ...
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15 votes

Password protected zip opened in notepad

First, there's no standard encoding for non-ASCII letters and several characters are not printable. At the very least you need a hex editor to view the information there. If you want to decipher the ...
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  • 38.6k
15 votes

How is malware distributed within zip files?

The same user who clicks on the ZIP-file to extract the JS-file also clicks the JS-file. This will launch the Windows Script Host to execute the script (it runs both JScript (JS and JSE) and VBScript ...
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  • 364
12 votes
Accepted

Is a ZIP file password easy to break?

The ZIP format supports several variants of password-protection of a file. The early password protection system in ZIP is known to be seriously flawed. However, later versions of the format provide ...
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  • 48.8k
12 votes
Accepted

Is it easier to crack a ZIP file than a 7z archived file given they have the same password?

It depends on how the ZIP file is encrypted. When you want to create a fully standard-compliant ZIP archive, then your only option for encryption is the ZipCrypto algorithm which is known to be ...
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  • 48.8k
11 votes

Is it possible to read a text file inside a password-protected zip file without the password?

No, nowadays zip files are protected by AES. This will hide all of the plaintext in a way that you can only recover it when you have the key. The only other thing you can see is the size of the ...
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10 votes

How is malware distributed within zip files?

Windows Script Host is an automation technology that provides scripting abilities. It is language-independent in that it can make use of different Active Scripting language engines. By default, ...
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10 votes
Accepted

How long should zip encryption password be for it take 10 years to crack?

If you are using ZipCrypto for encryption, then any password length is insecure. You are using the ZipCrypto cipher, rather than the more secure AES. ZipCrypto is extremely weak, as it is based ...
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  • 64k
9 votes
Accepted

How to detect zip file encryption algorithm

7Zip archiver (freeware) has an info button that among other useful things tell you the encryption type an archive is using. As a general note, .Zips usually use something called "ZipCrypto Deflatte"...
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  • 8,799
9 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

At the OS level, a file whatever is its content or structure is nothing more than a sequence of bytes. That means that the sequence of bytes can be read, encrypted and written again (in a crypted ...
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9 votes

Is it possible to read a text file inside a password-protected zip file without the password?

Unfortunately, not really. What you must understand here is that we are not speaking of a file that "is there", access to the original contents is not actively being blocked by the zip software you ...
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9 votes

How does a zip file detect a correct password?

The Cyclic Redundancy Check (CRC) field is used to determine whether or not the file is decrypted correctly. Quoted from the original ZIP format specification: After the header is decrypted, the ...
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  • 193
9 votes

At which point can a system be compromised when downloading archived data from an untrusted source?

In theory all of these places could be exploited. I am not going to go into specific exploits available as these change constantly with archive format and moving tech: Initially downloading and saving ...
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  • 399
8 votes

How to recover a lost zip file password?

Just wanted to add another method using fcrackzip CLI tool. It's in most Linux distro repos such as Ubuntu & Fedora/CentOS. Using it is pretty straightforward: $ fcrackzip -b -c a1:$% -l 1-6 -u ...
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  • 245
7 votes

Are .zip files used as a modern attack vector?

I still get a lot of email virus that use Zip archives as payload. Initially, virus authors would use Zip archives to evade detection by antivirus software that merely looks for executable files. ...
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7 votes

Is storing an encrypted zip file to an insecure cloud service an admissible way of securing privacy?

Privacy and confidentiality are different things... A Zip file, even encrypted, is still there, and onlookers may observe not only the archive presence, name and size, but also the individual names ...
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7 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

Think of your zip as a house (with your data inside the house). Your house has a locked door. The ransomware builds a house around your house with its own lock. You cannot get inside your house unless ...
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  • 171
7 votes

Can the content of a password protected zip file be known?

Yes. Aside from the fact that the filenames are unencrypted, the contents of a password-protected Zip file can be recovered if it uses the old, insecure ZipCrypto cipher which uses the insecure, non-...
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  • 64k
6 votes

PDF.zip file password forgotten and need to reset

Some Zip archives use the old PKZIP encryption, which uses a weak homemade stream cipher. The attack is described here (implementing it is a nice exercise for crypto students, by the way). Tools which ...
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6 votes

Gmail, Yahoo, Hotmail , and so on; How do they check the content of an attached password-protected archived file like Winrar?

They can't. Encryption is encryption. Email services won't spend time and energy trying to brute force your password, nor do I believe they would create backdoors for the sake of email. If they let ...
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  • 31.8k

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