HUDF Ransomware (.hudf Files)

HUDF Ransomware uses the AES-256 encryption algorithm. This STOP/Djvu family is one of the most popular infection!

You may be interested in taking a look at our other antivirus tools: Trojan Killer and Trojan Scanner.

Technical details:

NameHUDF Virus
FamilySTOP/Djvu Ransomware
File Extenstion.hudf
AlgorithmAES-256 encryption. If HUDF cannot establish a connection to crooks server before starting the encryption process, it uses the offline key. This key is the same for all victims(!), making it possible to decrypt .hudf files in the future.
RansomFrom $490 to $980 (in Bitcoins)
  1. ⮞ Can delete Volume Shadow copies to make victim’s attempts to restore data impossible;
  2. ⮞ Adds a list of domains to HOSTS file to block access to certain security-related sites;
  3. ⮞ Installs password-stealing Trojan on the system, like Azorult Spyware;
DistributionThird-party downloaders, installers, peer-to-peer networks, RDP exploits, etc.,
Other variants
  • Nnqp Ransomware (.nnqp encrypted files)
  • Xcmb Ransomware (.xcmb encrypted files)
  • Sbpg Ransomware (.sbpg encrypted files)

  • HUDF virus is a ransomware type that belongs to a STOP/Djvu family. Like with any other ransomware, it is aimed at your money. This malware encrypts your files with a pretty strong cipher and then asks you to pay the ransom (~$1000) for file decryption. To prevent the file decryption by the alternative ways, HUDF virus makes some changes to your system.

    These changes are related to the security settings. First, malware stops your Microsoft Defender and blocks the third-party security tool if you have one. Then, it changes the Group Policies to block the launch of the installation files of antivirus programs. The final step is blocking access to the websites that contain information about file decryption and malware removal. These changes may affect PC usage in the future, so it is better to remove them as soon as possible.

    A few words about the spreading ways of HUDF ransomware: this virus did not appear out of anywhere - you have likely installed it together with a program of some sort. “Free” programs, which must originally be paid, are created by unknown users. During the hacking process, they are free to add whatever to the executable code of their product - spyware, coin miners, ransomware, or stealer. It is better to avoid such risks, especially when you cannot punish those persons through the police, for example.

    Encryption process

    The HUDF ransomware uses the AES-256 encryption algorithm. That is not the strongest method, but it still provides an overwhelming amount of possible decryption keys. To brute force the 78-digit number of keys, you need 3.5 unvigintillion years (1*10^65), even if you use the most powerful regular PC. Quantum computers can show a bit better results, but it is still too slow to get your files back while you are alive.

    The exact algorithm of encryption is next: malware scans each folder for the files it is able to encrypt. Then, when it finds the target, it makes a copy of your file, removes the original one, encrypts the copy and leaves it instead of the removed original. Such a procedure is done to prevent the situation when you have already opened the file, so ransomware is not able to read it because of the Windows restrictions. To each encrypted copy, the virus adds the specific extension - ".hudf". Then, ransomware creates a _readme.txt file in the folder where the encrypted file is located, and goes to the next folder.

    .HUDF Files

    Such an encryption method can be exploited for file recovery. Since the original file is deleted, you may try to recover it using the file recovery tools. The less time is passed - the bigger the chance to get your files back, so hurry up!

    Another specific moment that can help you to use the files even after the encryption is the fact that HUDF ransomware encrypts only the first 150KB of each file. Hence, you can try to run a big file, such as video or music, without the encryption. Similar feature also works with other ransomware families - Dharma, Conti and Makop encrypt the same 150KB.

    The FBI believes that the HelloKitty cryptor is controlled by operators from Ukraine
    The FBI believes that the HelloKitty cryptor is controlled by operators from Ukraine

    Ransom note: _readme.txt

    Ransom note is the same for the whole ransomware family. In fact, it is one of the main signs of to which family the certain ransomware belongs. Here is the typical note for STOP/Djvu family:

    Don't worry. You can return all your files!
    All your files like photos, databases, documents and other important are encrypted with strongest encryption and unique key.
    The only method of recovering files is to purchase decrypt tool and unique key for you.
    This software will decrypt all your encrypted files.
    What guarantees you have?
    You can send one of your encrypted file from your PC and we decrypt it for free.
    But we can decrypt only 1 file for free. File must not contain valuable information.
    You can get and look video overview decrypt tool:
    Price of private key and decrypt software is $980.
    Discount 50% available if you contact us first 72 hours, that's price for you is $490.
    Please note that you'll never restore your data without payment.
    Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.
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