AHTW Virus (.AHTW File) 🔐 Decrypt Lost Data & Removal Guide

What is Ahtw virus?

Ahtw virus is a ransomware associated with the STOP/Djvu family, encrypts files on the victim’s computer and demands a ransom for the decryption tools. Our team discovered Ahtw while analyzing recently submitted malware samples on the VirusTotal platform. It’s important to note that this ransomware can be distributed alongside other malware, such as RedLine or Vidar.

Once this ransomware a computer, it adds the “.ahtw” extension to the filename of each encrypted file. For instance, a file named “1.jpg” becomes “1.jpg.ahtw“, “2.doc” transforms into “2.doc.ahtw“, and so on. Moreover, the ransomware generates a ransom note called “_readme.txt“.

I have prepared a comprehensive list of potential solutions, tips, and techniques that can help you effectively combat the Ahtw virus and recover your encrypted files. While in some cases file restoration can be a straightforward process, there are instances where retrieving the files may pose significant challenges.

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Ahtw

🤔 Ahtw virus is ransomware that originates from the DJVU/STOP family. Its primary purpose is to encrypt files that are important for you. After that ransomware virus asks its victims for a ransom fee ($490 – $980) in BitCoin.

The Ahtw virus employs a unique encryption key for each victim; however, there is a limitation to its encryption method:

If the Ahtw virus is unable to establish a connection with its command and control server (C&C Server) before starting the encryption process, it utilizes offline keys. These offline keys are the same for all victims, providing a potential avenue for decrypting files encrypted in a ransomware attack.

Ahtw virus is basically similar to other the same DJVU family: Ahui, Neqp, Nerz. The image below gives a clear vision of how the files with “.ahtw” extension look like:

Ahtw File (STOP/DJVU Ransomware)

Name	Ahtw Virus
Ransomware family¹	DJVU/STOP² ransomware
Extension	.ahtw
Ransomware note	_readme.txt
Ransom	From $490 to $980 (in Bitcoins)
Contact	[email protected], [email protected]
Detection	KillMBR.Trojan.MBRKiller.DDS, Trojan-PSW.Win32.Coins.pef, Win32:VB-ABLQ [Trj]
Symptoms	Encryption of the vast majority of your files. Malware mostly takes photos, videos, and documents, and appends a specific “.ahtw” extension to them. Volume Shadow copies removed, thereby rendering victims’ attempts to restore their data impossible. Modified HOSTS file by adding a list of domains. This blocks access to specific security-related websites. Installing a password-stealing Trojan, such as Vidar Stealer or RedLine Stealer, onto the infected system. Furthermore, it manages to implant a SmokeLoader backdoor as part of its malicious activities.
Fix Tool	To remove possible malware infections, scan your PC: 6-day free trial available.

This text asking payment is for restore files via decryption key:

_readme.txt (STOP/DJVU Ransomware) – The scary alert demanding from users to pay the ransom to decrypt the encoded files contains these frustrating warnings

The Ahtw ransomware carries out a series of processes to execute various tasks on the victim’s computer. One of the initial processes is winupdate.exe, which presents a deceptive Windows update prompt to the victim during the attack. This misleading tactic aims to make the victim believe that a sudden system slowdown is caused by a legitimate Windows update. Concurrently, another process with a randomly generated four-character name scans the system for target files and encrypts them. Additionally, the ransomware executes the following CMD command to delete Volume Shadow Copies:

vssadmin.exe Delete Shadows /All /Quiet

By removing the Volume Shadow Copies, the ransomware prevents the victim from restoring the computer to a previous state using System Restore Points. Ransomware operators deliberately eliminate Windows OS-based methods that could potentially aid in file restoration free of charge. Furthermore, the ransomware modifies the Windows HOSTS file by adding a list of domains and mapping them to the localhost IP. Consequently, when the victim tries to access any of the blocked websites, they will encounter a DNS_PROBE_FINISHED_NXDOMAIN error.

We observed that the ransomware attempts to block websites that provide instructional guides for computer users. This indicates that the cybercriminals aim to hinder the victim’s access to relevant and helpful information regarding ransomware attacks by restricting specific domains. The virus also creates two text files on the victim’s computer, bowsakkdestx.txt and PersonalID.txt, which contain attack-related details such as the victim’s public encryption key and personal ID.

After implementing these modifications, the malware continues to wreak havoc. Variants of the STOP/DJVU ransomware are known to deploy the Vidar password-stealing Trojan on compromised systems, which possesses an extensive range of capabilities, including:

Stealing login credentials for platforms like Steam, Telegram, and Skype.
Targeting cryptocurrency wallets for theft.
Downloading and executing malware on the infected computer.
Extracting sensitive information such as browser cookies, saved passwords, and browsing history.
Accessing and manipulating files on the victim’s computer.
Granting hackers remote control over the victim’s computer for various malicious activities.

The DJVU/STOP ransomware family employs the AES-256 encryption algorithm. Consequently, when malware encrypted the files using an offline decryption key, which is entirely unique, the unfortunate truth is that decrypting the files becomes an impossible task.

In the event that the Ahtw virus operated in online mode, gaining access to the AES-256 key becomes an unattainable feat. Hackers that stand behind the ransomware keep the key on their server.

To obtain the decryption key, victims should pay $980 and contact the hackers by the email address from the ransom note ([email protected]).

The message by the ransomware states the following information:

ATTENTION!

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:

https://we.tl/t-WJa63R98Ku

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.

To get this software you need write on our e-mail:

[email protected]

Reserve e-mail address to contact us:

[email protected]

Your personal ID:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Do not pay for ransom!

Please, try to use the available backups, or Decrypter tool

The _readme.txt file also indicates that the computer owners must get in touch with the Djvu ransomware representatives during 72 hours starting from the moment of files encryption. On the condition of getting in touch within 72 hours, users will have to pay only a half of the sum. Thus the ransom amount will be minimized down to $490. Yet, stay away from paying the ransom!

I insist that you do not contact these crooks and do not pay. The one of the most real working solution to recover the lost data – just using the available backups, or use Decrypter tool.

The peculiarity of all such viruses apply a similar set of actions for generating the unique decryption key to recover the ciphered data.

Thus, unless the ransomware is still under the stage of development or possesses with some hard-to-track flaws, manually recovering the ciphered data is a thing you can’t perform. The only solution to prevent the loss of your valuable data is to regularly make backups of your crucial files.

Note that if you do have regular backups, it is important to store them in a dedicated location separate from your main workstation, rather than keeping them connected to it.

For example, you can store the backup on a USB flash drive or an external hard drive. Alternatively, consider using online (cloud) storage services for your backup data.

It goes without saying that if you keep your backup data on your regular device, it is susceptible to encryption just like any other data.

For this reason, locating the backup on your main computer is surely not a wise idea.

How I was infected?

Ransomware has a various methods to built into your system. But it doesn’t really matter what way had place in your case.

Ransomware attack following a successful phishing attempt.

Nevertheless, these are the common leaks through which it may be injected into your PC:

hidden installation along with other apps, especially the utilities that work as freeware or shareware;
dubious link in spam emails leading to the virus installer
online free hosting resources;
using illegal peer-to-peer (P2P) resources for downloading pirated software.

There were cases when the Ahtw virus was hiding as some legitimate tool, for example, in the messages demanding to initiate some unwanted software or browser updates. This is typically the way how some online frauds aim to force you into installing the ransomware manually, by actually making you directly participate in this process.

Indeed, the fake update alert will not explicitly indicate that you are about to install the virus. Instead, it will have a disguise of, for example, an alert prompting you to update a program like Adobe Flash Player or another suspicious software.

Of course, the cracked apps represent the damage too. Using P2P is both illegal and may result in the injection of serious malware, including the Ahtw ransomware.

To sum up, what can you do to avoid the injection of the Ahtw ransomware into your device? Even though there is no 100% guarantee to prevent your PC from getting damaged, there are certain tips I want to give you to prevent the penetration. You must be cautious while installing free software today.

Make sure you always read what the installers offer in addition to the main free program. Stay away from opening dubious email attachments. Do not open files from the unknown addressees. And, of course, keep your security software up to date.

The malware does not speak openly about itself. It will not be mentioned in the list of your available programs. However, it will be masked under some malicious process running regularly in the background, starting from the moment when you launch your computer.

How To Remove Ahtw Virus?

In addition to encode a victim’s files, the Ahtw infection has also started to install the Vidar Stealer on computer to steal account credentials, cryptocurrency wallets, desktop files, and more.³

Reasons why I would recommend GridinSoft⁴

How To Decrypt .ahtw Files?

Restore solution for big “.ahtw files“

Try removing .ahtw extension on a few BIG files and opening them. Either the Ahtw read and did not encrypt the file, or it bugged and did not add the filemarker. If your files are very large (2GB+), the latter is most likely. Please, let me know in comments if that will work for you.

The newest extensions released around the end of August 2019 after the criminals made changes. This includes Neon, Weqp, Weon, etc.

As a result of the changes made by the criminals, STOPDecrypter is no longer supported. It has been removed and replaced with the Emsisoft Decryptor for STOP Djvu Ransomware developed by Emsisoft.

You can download free decryption tool here: Decryptor for STOP Djvu.

Select folders for decryption.

Based on the default settings, the decryptor will automatically populate the available locations in order to decrypt the currently available drives (the connected ones), including the network drives. Additional locations can be selected with the help of the “Add” button.

Decryptors normally suggest several options considering the specific malware family. The current possible options are presented in the Options tab and can be activated or deactivated there. You may locate a detailed list of the currently active Options below.

Click on the “Decrypt” button.

As soon as you add all the desired locations for decryption into the list, click on the “Decrypt” button in order to initiate the decryption procedure.

Note that the main screen may turn you to a status view, letting you know of the active process and the decryption statistics of your data:

The decryptor will notify you as soon as the decryption procedure is completed. If you need the report for your personal papers, you can save it by choosing the “Save log” button. Note that it is also possible to copy it directly to your clipboard and to paste it into emails or messages here if you need to do so.

The Emsisoft Decryptor might display different messages after a failed attempt to restore your ahtw files:

✓ Error: Unable to decrypt file with ID: [your ID]

There is no corresponding decryption key in the Emsisoft decryptor’s database.

✓ No key for New Variant online ID: [your ID]

Notice: this ID appears to be an online ID, decryption is impossible

Your original files were encrypted with an online key. So no one else has the same encryption/decryption key pair. Recovery of ahtw files without paying the criminals is impossible. 🙁

✓ Result: No key for new variant offline ID: [example ID]

This ID appears be an offline ID. Decryption may be possible in the future.

An offline key was used, but files could not be restored (the offline decryption key isn’t available yet). But, receiving this message is good news for you, because it might be possible to restore your ahtw files in the future. 🙂
It can take a few weeks or months until the decryption key gets found and uploaded to the decryptor. Please follow updates regarding the decryptable DJVU versions here.

✓ Remote name could not be resolved

It’s an indication of a DNS issue on your PC. Our first recommendation is to reset your HOSTS file back to default.

How to Restore .ahtw Files?

In some case Ahtw ransomware is not doom for your files…

The encryption mechanism is next: it encrypts every file byte-by-byte, then saves a file copy, deleting (and not overriding!) the original file. Hence, the information of the file location on the physical disk is lost, but the original file is not deleted from the physical disk. The cell, or the sector where this file was stored, can still contain this file, but it is not listed by the file system and can be overwritten by data that has been loaded to this disk after the deletion. Hence, it is possible to recover your files using special software.

I recently had my pc infected by the Ahtw virus. It managed to bypass 2 Antivirus software and 2 malware fighters.

Anyway, after realizing it was an online algorithm, it is impossible to retrieve my encrypted files. I also had my backup drive plugged in at the time of the virus, and this was also infected, or so I thought. Every folder within my backup drive had been infected and was encrypted. However, despite losing some important files, I retrieved almost 80% of my 2TB storage.

When I started going through the folders, I noticed the readme.txt ransom note in every folder. I opened some of the folders and found that all files that were not in a subfolder within that folder had been encrypted. However, I found a flaw and glimmer of hope when I went into the subfolders in other folders and found that these files had not been encrypted. Every folder within my c and d drives, including subfolders, had been encrypted, but this was not the case with the backup drive. Having subfolders created within a folder has saved 80% of my data.

As I said, I believe this to be only a small loophole on a backup drive. I’ve since found a further 10 % of my data on another hard drive on a different pc. So my advice is if you use a backup drive, create subfolders. I was lucky, I guess. But I was also unlucky that the virus hit as I was transferring some files from my backup.

Hopefully, this can help some other people in my situation.

Jamie Newland

Some pointers for recovery repair of Ahtw files (true for all STOP/DJVU variants):

I have seen Ahtw variants fail to encrypt deeper nested folders, so that you can check that. You may find those are not encrypted.

This ransomware saves encrypted data to a new file, deletes the original. So there’s a slight chance part of that deleted file can be recovered using file recovery software. It’s unlikely the folder structure can be restored, so a free tool like PhotoRec may be as good as any.

This ransomware only partially encrypts (about the first 150 KB), so depending on file size and type of data, the not encrypted part may be recoverable.

Joep

Recovering your files with PhotoRec

PhotoRec is a program that originated as an open-source tool for recovering files from damaged disks or for retrieving deleted files. Over time, it has evolved to support the recovery of files with over 400 different extensions, making it suitable for data recovery after a ransomware attack.

To begin, you will need to download this application. It is completely free, although the developer cautions that there is no guarantee of file recovery. PhotoRec is bundled with another utility from the same developer called TestDisk. When you download the archive, it will be named TestDisk, but rest assured that PhotoRec files are included.

To access PhotoRec, locate and open the “qphotorec_win.exe” file. No installation is required, as the program contains all the necessary files within the archive. This means you can store it on a USB drive and use it to assist friends, family, or anyone affected by the DJVU/STOP ransomware.

After the launch, you will see the screen showing you the full list of your disk spaces. However, this information is likely useless, because the required menu is placed a bit higher. Click this bar, then choose the disk which was attacked by ransomware.

After choosing the disk, you need to choose the destination folder for the recovered files. You will find this menu at the lower part of the PhotoRec window. The best desicion is to export them on USB drive or any other type of removable disk.

Then, you need to specify the file formats. This option is at the interface bottom, too. As I have mentioned, PhotoRec can recover the files of about 400 different formats.

Finally, you can start files recovery by pressing the “Search” button. You will see the window with scan and recovery results.

Ahtw files recovery guide

Frequently Asked Questions

🤔 How can I open “.ahtw” files?

No way. These files are encrypted by ransomware. The contents of encrypted files are not available until they are decrypted.

🤔 My files contain important information. How can I decrypt them urgently?

It is highly recommended that you check if you have a backup copy available. If not, then you can try to restore them through the system function – Restore Point. All other methods will require patience.

🤔 You have advised using GridinSoft Anti-Malware to remove ransomware. Does this mean that the program will delete my encrypted files?

Of course not. Your encrypted files do not pose a threat to the computer. What happened has already happened.

🤔 Ahtw virus has blocked infected PC: I can’t get the activation code.

In this situation, you need to prepare the memory stick with a pre-installed

🤔 Decryptor did not decrypt all my files, or not all of them were decrypted. What should I do?

Have patience. Ahtw is the newest Djvu ransomware variant, and analysts still seek for the decryption keys. Follow the news on our website. We will keep you posted on when new keys or new decryption programs appear.

🤔 What can I do right now?

The Ahtw ransomware encrypts only the first 150KB of files. So MP3 files are rather large, some media players (Winamp for example) may be able to play the files, but – the first 3-5 seconds (the encrypted portion) will be missing. You can try to find a copy of an encrypted file: Download the files you’ve got from the Internet before the attack.