FacebookTwitterLinkedIn

How to eliminate Koom ransomware from a computer?

Also Known As: Koom virus
Damage level: Severe

What is Koom ransomware?

Koom encrypts files so that victims could not access them without a decryption tool purchased from the attackers. It also appends the ".koom" extension to filenames (for example, it changes a file named "1.jpg" to "1.jpg.koom", "2.jpg" to "2.jpg.koom"), and creates a ransom note (the "_readme.txt" file). Koom is part of the Djvu ransomware family.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

Koom decrypt instructions (_readme.txt)

Koom ransom note overview

The "_readme.txt" file is created to inform victims that all their files are encrypted with the strongest encryption algorithm and cannot be decrypted without the right decryption tool and unique key. Decryption tools cost $980 (but can be purchased for $490 if victims contact the attackers within 72 hours from the attack).

Instructions on how to purchase decryption tools will be provided after contacting the attackers via manager@mailtemp.ch or managerhelper@airmail.cc. Before paying a ransom, victims can send one file that does not contain valuable data and is no larger than one megabyte. Victims are offered to receive that file decrypted for free.

More details about ransomware

Typically, files encrypted by ransomware cannot be decrypted without a tool (program, key) that only the attackers can provide. Victims can avoid paying a ransom if they have their files backed up or a free decryption tool is available on the Internet. A ransom should not be paid - the attackers may not send a decryption tool even after the payment.

Ransomware should be uninstalled from the infected computer as soon as possible - it may cause more damage by encrypting new files and (or) infecting computers on the local network. Files remain encrypted even after the uninstallation of ransomware that has encrypted them.

Similarities with other ransomware variants

Most ransomware variants encrypt files and generate a ransom note with contact and payment information (and other details). Victims are forced to purchase a decryption tool from the attackers to restore access to files. More ransomware examples are Delta Plus, yUixN, and JamesBond.

How did ransomware infect my computer?

Most ransomware variants are distributed through emails, Trojans, fake software updaters, unreliable sources for downloading files, programs or software cracking tools. Users install ransomware through emails by opening malicious attachments or files downloaded via received website links.

Ransomware gets installed through Trojans when they are designed to install their payload (cause chain infections). Users install Trojans in the ways described in this section. Fake software updaters install ransomware instead of updates or fixes for installed software or exploit flaws of outdated software.

Ransomware gets installed through unreliable sources for downloading files, programs when users open malicious downloads. Software cracking tools infect systems when they are designed to install malware instead of illegally activating licensed software.

Threat Summary:
Name Koom virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .koom
Ransom Demanding Message _readme.txt
Free Decryptor Available? Partial (more information below).
Ransom Amount $980/$490
Cyber Criminal Contact manager@mailtemp.ch, managerhelper@airmail.cc
Detection Names Avast (FileRepMalware), AVG (FileRepMalware), Ikarus (Trojan.Win32.Glupteba), Kaspersky (UDS:Exploit.Win32.Shellcode.gen), Microsoft (Trojan:Win32/CryptInject.FB!MTB), Full List Of Detections (VirusTotal)
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below).
Distribution methods Infected email attachments (macros), torrent websites, malicious ads.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.
Malware Removal (Windows)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner.
▼ Download Combo Cleaner
To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.

How to protect yourself from ransomware infections?

Email attachments in irrelevant emails sent from unknown or suspicious addresses should not be opened. Website links in emails of this kind should not be clicked as well. Files and applications should be downloaded only from official pages and via direct links.

Installed programs must be activated and (or) updated with tools provided by their official developers. The operating system should be scanned for threats regularly. It is recommended to scan it with reputable anti-spyware or antivirus software and keep that software up to date.

If your computer is already infected with Koom, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.

Text presented in Koom ransomware's text file ("_readme.txt"):

ATTENTION!

Don't worry, you can return all your files!
All your files like pictures, 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:
hxxps://we.tl/t-vtoEIhR0SI
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:
manager@mailtemp.ch

Reserve e-mail address to contact us:
managerhelper@airmail.cc

Your personal ID:
-

Screenshot of files encrypted by Koom (".koom" extension):

Files encrypted by Koom ransomware (.koom extension)

Screenshot of fake Windows update pop-up displayed during the encryption:

Fake Windows pop-up displayed by Koom during the encryption

IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list.

Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).

Screenshot of websites added to Windows hosts file:

Tro Ransomware adding websites to Windows Hosts file

There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding.

Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore.

If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.

Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:

Djvu ransomware decrypter by Michael Gillespie and Emsisoft

Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption. All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files).

Note that the file processing may take some time so be patient. It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.

Screenshot of Emsisoft's Djvu decryption service page:

Djvu ransomware decryption service by Emsisoft

Some victims state that they've successfully restored a part of encrypted data using PhotoRec tool developed by CGSecurity (Christophe Grenier). You can download this tool from CGSecurity's official website.

Screenshot of PhotoRec application:

PhotoRec restoration tool for Stop/Djvu ransomware

Now it is worth noting that Djvu ransomware does not encrypt the entire file. Instead, it encrypts only a portion (start) of the file, thereby making it unusable. Luckily, in some cases it is possible to restore other part of the file, which is not encrypted. This is useful when it comes to audio/video files, because even though the start won't be restored, you'll still be able to use most of it.

To restore audio/video data we advise you to use Media_Repair tool developed by DiskTuna. This tool is extremely simple and completely free. You can find the user manual as well as download the tool directly from DiskTuna's website.

Screenshot of Media_Repair application developed by DiskTuna:

Media_Repair application by DiskTura restoring audio/video files encrypted by Stop/Djvu ransomware

Koom ransomware removal:

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
▼ DOWNLOAD Combo Cleaner By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.

Video suggesting what steps should be taken in case of a ransomware infection:

Quick menu:

Reporting ransomware to authorities:

If you are a victim of a ransomware attack we recommend reporting this incident to authorities. By providing information to law enforcement agencies you will help track cybercrime and potentially assist in the prosecution of the attackers. Here's a list of authorities where you should report a ransomware attack. For the complete list of local cybersecurity centers and information on why you should report ransomware attacks, read this article.

List of local authorities where ransomware attacks should be reported (choose one depending on your residence address):

Isolating the infected device:

Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.

Step 1: Disconnect from the internet.

The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:

Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result: Disconnecting computer from the Internet (step 1)

Click the "Change adapter settings" option in the upper-left corner of the window: Disconnecting computer from the Internet (step 2)

Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable". Disconnecting computer from the Internet (step 3)

Step 2: Unplug all storage devices.

As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:

Navigate to "My Computer", right-click on each connected device, and select "Eject": Ejecting external storage devices

Step 3: Log-out of cloud storage accounts.

Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.

Identify the ransomware infection:

To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).

Identify ransomware-type infection (step 1)

This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).

Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).

Identify ransomware-type infection (step 2)

This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.

One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).

Identify ransomware-type infection (step 3)

The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.

Example 1 (Qewe [Stop/Djvu] ransomware):

Identify ransomware-type infection (step 4)

Example 2 (.iso [Phobos] ransomware):

Identify ransomware-type infection (step 5)

If your data happens to be encrypted by ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, a ransom message title, file extension, provided contact emails, crypto wallet addresses, etc.).

Search for ransomware decryption tools:

Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cybercriminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.

Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.

Searching for ransomware decryption tools in nomoreransom.org website

Restore files with data recovery tools:

Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use the Recuva tool developed by CCleaner. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data). In addition, the recovery feature is completely free.

Step 1: Perform a scan.

Run the Recuva application and follow the wizard. You will be prompted with several windows allowing you to choose what file types to look for, which locations should be scanned, etc. All you need to do is select the options you're looking for and start the scan. We advise you to enable the "Deep Scan" before starting, otherwise, the application's scanning capabilities will be restricted.

Recuva data recovery tool wizard

Wait for Recuva to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundred gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process:

Recuva data recovery tool scan time

Step 2: Recover data.

Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data:

Recuva data recovery tool recovering data

Create data backups:

Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.

Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all the necessary information on Microsoft's documentation web page.

Data backups: One of the most reliable backup methods is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from the sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach, although it's a really rare occasion.

We recommend using Microsoft OneDrive for backing up your files. OneDrive lets you store your personal files and data in the cloud, sync files across computers and mobile devices, allowing you to access and edit your files from all of your Windows devices. OneDrive lets you save, share and preview files, access download history, move, delete, and rename files, as well as create new folders, and much more.

You can back up your most important folders and files on your PC (your Desktop, Documents, and Pictures folders). Some of OneDrive’s more notable features include file versioning, which keeps older versions of files for up to 30 days. OneDrive features a recycling bin in which all of your deleted files are stored for a limited time. Deleted files are not counted as part of the user’s allocation.

The service is built using HTML5 technologies and allows you to upload files up to 300 MB via drag and drop into the web browser or up to 10 GB via the OneDrive desktop application. With OneDrive, you can download entire folders as a single ZIP file with up to 10,000 files, although it can’t exceed 15 GB per single download.

OneDrive comes with 5 GB of free storage out of the box, with an additional 100 GB, 1 TB, and 6 TB storage options available for a subscription-based fee. You can get one of these storage plans by either purchasing additional storage separately or with Office 365 subscription.

Creating a data backup:

The backup process is the same for all file types and folders. Here’s how you can back up your files using Microsoft OneDrive

Step 1: Choose the files/folders you want to backup.

Click the OneDrive icon in the taskbar

Click the OneDrive cloud icon to open the OneDrive menu. While in this menu, you can customize your file backup settings.

Select Help & Settings and click Settings

Click Help & Settings and then select Settings from the drop-down menu.

Select the Backup tab and click Manage backup

Go to the Backup tab and click Manage backup.

Select folders to backup and click Start backup

In this menu, you can choose to backup the Desktop and all of the files on it, and Documents and Pictures folders, again, with all of the files in them. Click Start backup.

Now, when you add a file or folder in the Desktop and Documents and Pictures folders, they will be automatically backed up on OneDrive.

To add folders and files, not in the locations shown above, you have to add them manually.

Select a file manually and copy it

Open File Explorer and navigate to the location of the folder/file you want to backup. Select the item, right-click it, and click Copy.

Paste the copied file in the OneDrive folder to create a backup

Then, navigate to OneDrive, right-click anywhere in the window and click Paste. Alternatively, you can just drag and drop a file into OneDrive. OneDrive will automatically create a backup of the folder/file.

File statuses in OneDrive folder

All of the files added to the OneDrive folder are backed up in the cloud automatically. The green circle with the checkmark in it indicates that the file is available both locally and on OneDrive and that the file version is the same on both. The blue cloud icon indicates that the file has not been synced and is available only on OneDrive. The sync icon indicates that the file is currently syncing.

Click Help & Settings and click View Online

To access files only located on OneDrive online, go to the Help & Settings drop-down menu and select View online.

Click the Settings cog and click Options

Step 2: Restore corrupted files.

OneDrive makes sure that the files stay in sync, so the version of the file on the computer is the same version on the cloud. However, if ransomware has encrypted your files, you can take advantage of OneDrive’s Version history feature that will allow you to restore the file versions prior to encryption.

Microsoft 365 has a ransomware detection feature that notifies you when your OneDrive files have been attacked and guide you through the process of restoring your files. It must be noted, however, that if you don’t have a paid Microsoft 365 subscription, you only get one detection and file recovery for free.

If your OneDrive files get deleted, corrupted, or infected by malware, you can restore your entire OneDrive to a previous state. Here’s how you can restore your entire OneDrive:

restore-your-onedrive

1. If you're signed in with a personal account, click the Settings cog at the top of the page. Then, click Options and select Restore your OneDrive.

If you're signed in with a work or school account,  click the Settings cog at the top of the page. Then, click Restore your OneDrive.

2. On the Restore your OneDrive page, select a date from the drop-down list. Note that if you're restoring your files after automatic ransomware detection, a restore date will be selected for you.

3. After configuring all of the file restoration options, click Restore to undo all the activities you selected.

The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.

Frequently Asked Questions (FAQ)

How was my computer hacked and how did hackers encrypt my files?

Ransomware is distributed in various ways (for example, malicious emails, drive-by downloads). In case of Stop/Djvu ransomware, cyber criminals often hide their ransomware executables in download pages for cracked software (or cracking tools that are supposed to activate software). By using them users infect computers with malware by themselves.

How to open ".koom" files?

Once files are encrypted by ransomware, they cannot opened until they are decrypted with the right tool.

How can I decrypt ".koom" files for free?

Usually, Stop/Djvu ransomware variants encrypt files using an online key. In this particular case it is impossible to decrypt files without using a tool provided by the attackers behind Koom. Sometimes, ransomware encrypts files using an offline key. Then it is possible to decrypt files with Emsisoft's Djvu decryption software (more information above).

Should I pay a ransom?

Paying a ransom is not recommended. Paying a ransom means supporting cyber criminal. Also,  there are no guarantees that the attackers will send a decryption tool (software, key).

Will Combo Cleaner help me remove Koom ransomware?

Yes, Combo Cleaner will scan your computer and eliminate active ransomware infections. However, eliminating ransomware with antivirus program is the first step in the recovery process. Security software cannot decrypt files encrypted by ransomware (in this case, Koom).

Click to post a comment

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

Our malware removal guides are free. However, if you want to support us you can send us a donation.

About PCrisk

PCrisk logo

PCrisk is a cyber security portal, informing Internet users about the latest digital threats. Our content is provided by security experts and professional malware researchers. Read more about us.

Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
Koom virus QR code
Scan this QR code to have an easy access removal guide of Koom virus on your mobile device.
We Recommend:

Get rid of Windows malware infections today:

▼ REMOVE IT NOW
Download Combo Cleaner

Platform: Windows

Editors' Rating for Combo Cleaner:
Editors ratingOutstanding!

[Back to Top]

To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.