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Sigma ransomware virus. How to remove? (Uninstall guide)

removal by Julie Splinters - - | Type: Ransomware
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Sigma ransomware presents peculiar details

The screenshot of Sigma malware

Sigma virus functions as a new file-encrypting threat. The very modus operandi is similar to other crypto-malware: it encrypts important documents using RSA-2048 and adds random 4-character file extension.

During the process, it places ReadMe.html file which directs users to an online payment site. It briefly informs users about the encrypted data. It instructs them to download TorBrowser and access the specific .onion page.[1] The latter presents a page entitled a “Sigma Ransomware” and asks to enter machine GUID. It also includes a link to download the GUID Helper.

After the encryption is finished, the malware also changes the desktop background. The message urges users to find “Readme” file or visit the mentioned .onion link and enter the personal ID number indicated on the ransom note. On the desktop, Sigma ransomware also leaves GUID.exe and GUID.txt files.

Speaking of the payment site, it consists of several pages. One of them indicated the exact time when your files were encrypted. It demands $1000 for the decryption software. If payment is not remitted within 7 days, the ransom amount will double. On the same .onion page, victims are encouraged to create Bitcoin wallet.

Unlike standard ransomware, Sigma crypto-malware does not provide an email address but instead suggests using Xamp account. It also includes Pidgin Installation Guide link. Therefore, they contact the perpetrator via Sigmaxxx@jabb.im[2] address.

Instead of complying with the demands, remove Sigma ransomware. You can do so with the assistance of Reimage or Malwarebytes Anti Malware. You might need to boot your computer into Safe Mode. Further instructions are indicated below.

At the moment, the malware has a low detection ratio. It is spreads disguised as Automated Universal MultiBoot UFD Creation Tool.exe file or Guid.exe.bin. It is detectable as Trojan.Agent.CPOW,[3], Trojan.Ransom.Shade!1.A988 (CLASSIC), etc. The former sample is only identified by one security tool as Trojan.Generic.bcnxb[4] file. Observing the former alternative trojan name and the very design of the ransom note, it is possible to assume its relation to Shade malware.

Furthermore, the malware also reads technical computer details, particularly RDP protocols. It also creates a counterfeited system process to disguise its activity. Interestingly, the malware has anti-sandboxing features. It maneuvers to escape the detection. If the occupied system happens to be natural OS environment rather than a virtual machine, the malware then connects to http://ip.api/json.txt[2] and send the data about victim’s geolocation.

Spam emails with the “unlock” code

While the malware presents detailed GUI and payment sites, its distribution campaign is quite distinctive than other crypto-malware. Sigma malware is delivered in a spam email attachment “Scan_[number].doc” file.

The email message briefly states the that the receiver is going to be billed [money amount] on their personal Mastercard balance right away. In order to avoid it, they should review the attachment. It also includes a passcode. However, entering the code activates Sigma hijack. Interestingly, though the malware is written in English, it was spotted in Greek[5] domains.

Besides spam emails, users should be also vigilant while downloading applications. Pay attention to what source you download it and whether it is certified. Pay attention to the installation wizard stages to deselect optional and unnecessary add-ons. Now let us move to Sigma removal section.

Eliminate Sigma crypto-virus from Windows

The malware is indeed well-programmed. At the moment, there is little information about any ransom payment. There are no guarantees that the felons will return all and undamaged files. Instead, focus on Sigma removal.

You may do so with the assistance of malware elimination tool. In case you cannot launch to remove Sigma virus, perform System Restore or restart the computer in Safe Mode. Only after the eliminate the malware, proceed to data recovery.

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What to do if failed?
If you failed to remove infection using Reimage, submit a question to our support team and provide as much details as possible.
Reimage is recommended to uninstall Sigma ransomware virus. Free scanner allows you to check whether your PC is infected or not. If you need to remove malware, you have to purchase the licensed version of Reimage malware removal tool.

More information about this program can be found in Reimage review.

More information about this program can be found in Reimage review.

Manual Sigma virus Removal Guide:

Remove Sigma using Safe Mode with Networking

Reimage is a tool to detect malware.
You need to purchase Full version to remove infections.
More information about Reimage.

  • Step 1: Reboot your computer to Safe Mode with Networking

    Windows 7 / Vista / XP
    1. Click Start Shutdown Restart OK.
    2. When your computer becomes active, start pressing F8 multiple times until you see the Advanced Boot Options window.
    3. Select Safe Mode with Networking from the list Select 'Safe Mode with Networking'

    Windows 10 / Windows 8
    1. Press the Power button at the Windows login screen. Now press and hold Shift, which is on your keyboard, and click Restart..
    2. Now select Troubleshoot Advanced options Startup Settings and finally press Restart.
    3. Once your computer becomes active, select Enable Safe Mode with Networking in Startup Settings window. Select 'Enable Safe Mode with Networking'
  • Step 2: Remove Sigma

    Log in to your infected account and start the browser. Download Reimage or other legitimate anti-spyware program. Update it before a full system scan and remove malicious files that belong to your ransomware and complete Sigma removal.

If your ransomware is blocking Safe Mode with Networking, try further method.

Remove Sigma using System Restore

Reimage is a tool to detect malware.
You need to purchase Full version to remove infections.
More information about Reimage.

  • Step 1: Reboot your computer to Safe Mode with Command Prompt

    Windows 7 / Vista / XP
    1. Click Start Shutdown Restart OK.
    2. When your computer becomes active, start pressing F8 multiple times until you see the Advanced Boot Options window.
    3. Select Command Prompt from the list Select 'Safe Mode with Command Prompt'

    Windows 10 / Windows 8
    1. Press the Power button at the Windows login screen. Now press and hold Shift, which is on your keyboard, and click Restart..
    2. Now select Troubleshoot Advanced options Startup Settings and finally press Restart.
    3. Once your computer becomes active, select Enable Safe Mode with Command Prompt in Startup Settings window. Select 'Enable Safe Mode with Command Prompt'
  • Step 2: Restore your system files and settings
    1. Once the Command Prompt window shows up, enter cd restore and click Enter. Enter 'cd restore' without quotes and press 'Enter'
    2. Now type rstrui.exe and press Enter again.. Enter 'rstrui.exe' without quotes and press 'Enter'
    3. When a new window shows up, click Next and select your restore point that is prior the infiltration of Sigma. After doing that, click Next. When 'System Restore' window shows up, select 'Next' Select your restore point and click 'Next'
    4. Now click Yes to start system restore. Click 'Yes' and start system restore
    Once you restore your system to a previous date, download and scan your computer with Reimage and make sure that Sigma removal is performed successfully.

Bonus: Recover your data

Guide which is presented above is supposed to help you remove Sigma from your computer. To recover your encrypted files, we recommend using a detailed guide prepared by 2-spyware.com security experts.

If your files are encrypted by Sigma, you can use several methods to restore them:

Data Recovery Pro method

Though this software is designed to recover files after a system crash, it might prove to be effective in this case as well.

The benefits of ShadowExplorer

There are no reports about Sigma ransomware deleting shadow volume copies, so this software might help you recover some of the files by using the mentioned copies.

  • Download Shadow Explorer (http://shadowexplorer.com/);
  • Follow a Shadow Explorer Setup Wizard and install this application on your computer;
  • Launch the program and go through the drop down menu on the top left corner to select the disk of your encrypted data. Check what folders are there;
  • Right-click on the folder you want to restore and select “Export”. You can also select where you want it to be stored.

Sigma Decryptor

At the moment, there is no free decryption software released for this ransomware variant. It is not recommended  to use the one offered by the malwrae developers as it may only facilitate future hijack of the operating system.

Finally, you should always think about the protection of crypto-ransomwares. In order to protect your computer from Sigma and other ransomwares, use a reputable anti-spyware, such as Reimage, Plumbytes Anti-MalwareWebroot SecureAnywhere AntiVirus or Malwarebytes Anti Malware

About the author

Julie Splinters - Malware removal specialist

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