A new type of Trojan has been reported to utilize an old devastating method that corrupts Windows and restarts the computer. The Trojan is known as Disakil (Symantec), and it is not very widespread. However, this particular Trojan horse may be devastating to your hard drive. In case, you try to boot your system, and you see the “BOOTMGR is Missing” message, chances are you have been hit by the variants of this malware. In case this is true, you should not format your drive and look for alternatives to salvage your data.
| Name | KillDisk Disakil |
| Type | KillDisk Trojan |
| Short Description | The cyber-threat directly compromises the operating system and files below 1.1 MB of the infected PC. |
| Symptoms | The user may witness sudden restart after which his OS may fail to start and display a DOS error message instead. (ex. “BOOTMGR is missing”) |
| Distribution Method | Via other malware on the computer or the below mentioned methods in the “Distribution” paragraph. |
| Detection Tool | Download Malware Removal Tool, to See If Your System Has Been Affected by malware |
| User Experience | Join our forum to discuss KillDisk Disakil. |
KillDisk Disakil Trojan – Spread
Similar to every other Trojan Horse out there, this one may be distributed via four different ways:
- Via other malware or unwanted software installed on your computer.
- Via malicious URLs.
- Through malicious email or other messages’ attachments.
- If someone deliberately installed in on the computer.
KillDisk Disakil Trojan In Detail
Symantec Security Response researchers have established that its malicious executable that carries the payload has been downloaded and ran on the victim’s computer, the Trojan begins by making a .tmp file with random numbers or letters or both. The file is located in the %Temp% folder. KillDisk Disakil then deletes this subkey from the Windows Registry:
→“HKEY_LOCAL_MACHINE\Software\MicrosoftApplicationMgr”
After doing so, the malware begins to overwrite files. First, it overwrites a chunk of the data at the start of a file, called sec_service.exe.
After doing so, it begins to target smaller than 1.1 MB in case they are located in removable as well as fixed drives. The files it may target and overwrite may be of the following extensions:
→.accdb .bin .bmp .boot .cfg .crt .db .dbf .djvu .doc .docx .exe .ini .iso .jar .jpeg .jpg .lib .mdb .mdf .msi .pdf .ppt .pptx .rar .rtf .sql .tib .tiff .txt .vhd .xls .xlsx .xml .zip
The cyber-threat will also begin to overwrite bytes of the data in vital files that are located in the %Windows%. It targets these extensions:
→.dll .exe .xml .ttf .nfo .fon .ini .cfg .boot .jar
Meanwhile, this nasty malware may begin to end important processes. It leaves only some of them intact so that it can operate:
→ 73.exe audiodg.exe conhost.exe csrss.exe dwm.exe explorer.exe komut.exe lsass.exe lsm.exe services.exe shutdown.exe smss.exe spoolss.exe spoolsv.exe svchost.exe taskhost.exe wininit.exe winlogon.exe wuauclt.exe
Finally, this malware is capable of performing malicious activities on the computer. They may vary:
- Delete or modify the data in a service, called sec_service.
- Terminate sec_service and make it inactive.
- Delete the MBR(Master Boot Record) of the drives on the compromised PC, hence render them unusable.
- Erase the logs of the apps, security settings, setups, system events.
- Reset your computer.
These modifications may result in the destruction of the affected operating system by simply rendering system files unusable.
Remove KillDisk Trojan and Protect Your Files
Since this Trojan corrupts Windows, you have two primary options. Before seeing them, you must backup all of your data. To do this, you should seek to boot a live operating system that can unlock files on your drives without having access to them. One example of such Windows OS is originating from Russia and is called Windows 7 LiveCD by Xemom1. In it, the OS has an embedded AntiWinlocker, which will allow you to access your files. Bear in mind that this is just an example and it may not be safe for work. There are many other live OS’s out there that also have AntiWinlocker. Google is your friend.
Option 1: To try and repair your Windows OS.
To do that, you need to boot into the Advanced options menu and select the Repair your PC option. Here are instructions on how to work with the Advanced Startup Menu. From there, in the advanced menu, you should see several restoration options. From them, choose Advanced Options>Startup Repair. But to restore from an image or any other way you must have the original Windows CD with you.
Option 2: To extract your files and completely reinstall Windows OS.
This option is the easier one. Simply copy your files using a live OS (as the example above) and reinstall Windows by again booting in the advanced startup menu, but, this time, choosing the Reset Your PC preference.
Ofcourse you may try to boot in Safe Mode and scan your computer using an anti-malware tool which will remove the Trojan before attempting the methods above. This can happen if you go to Advanced Options>Startup Settings and select Safe Mode. You may still try doing this it is highly unlikely that you will succeed, so we recommend just to copy your data and reinstall Windows just to be safe. And then download a reliable anti-malware tool which will protect your computer from attacks by a KillDisk Trojan in the future.
N.B. In case you manage to find your files, and they are damaged, try repairing your Windows without formatting your hard drive and then try to restore earlier versions. Here are several file recovery options:
Also, to protect your files in the future, we have prepared instructions on how to back them up the proper way:
Back up your data to secure it against attacks in the future
IMPORTANT! Before reading the Windows backup instructions, we highly recommend to back up your data automatically with cloud backup and insure it against any type of data loss on your device, even the most severe. We recommend reading more about and downloading SOS Online Backup .
To back up your files via Windows and prevent any future intrusions, follow these instructions:
1. For Windows 7 and earlier 1. For Windows 8, 8.1 and 10 1. Enabling the Windows Defense Feature (Previous Versions)1-Click on Windows Start Menu
2-Type Backup And Restore
3-Open it and click on Set Up Backup
4-A window will appear asking you where to set up backup. You should have a flash drive or an external hard drive. Mark it by clicking on it with your mouse then click on Next.
5-On the next window, the system will ask you what do you want to backup. Choose the ‘Let Me Choose’ option and then click on Next.
6-Click on ‘Save settings and run backup’ on the next window in order to protect your files from possible attacks by KillDisk Disakil.
2-In the window type ‘filehistory’ and press Enter
3-A File History window will appear. Click on ‘Configure file history settings’
4-The configuration menu for File History will appear. Click on ‘Turn On’. After its on, click on Select Drive in order to select the backup drive. It is recommended to choose an external HDD, SSD or a USB stick whose memory capacity is corresponding to the size of the files you want to backup.
5-Select the drive then click on ‘Ok’ in order to set up file backup and protect yourself from KillDisk Disakil.
1- Press Windows button + R keys.
2- A run windows should appear. In it type ‘sysdm.cpl’ and then click on Run.
3- A System Properties windows should appear. In it choose System Protection.
5- Click on Turn on system protection and select the size on the hard disk you want to utilize for system protection.
6- Click on Ok and you should see an indication in Protection settings that the protection from KillDisk Disakil is on.
Restoring a file via Windows Defense feature:
1-Right-click on the damaged file, then choose Properties.
2-Click on the Previous Versions tab and then mark the last version of the file.
3-Click on Apply and Ok and the file damaged by KillDisk Disakil should be restored.
Ventsislav Krastev
Ventsislav is a cybersecurity expert at SensorsTechForum since 2015. He has been researching, covering, helping victims with the latest malware infections plus testing and reviewing software and the newest tech developments. Having graduated Marketing as well, Ventsislav also has passion for learning new shifts and innovations in cybersecurity that become game changers. After studying Value Chain Management, Network Administration and Computer Administration of System Applications, he found his true calling within the cybersecrurity industry and is a strong believer in the education of every user towards online safety and security.
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