How to remove Sigrun ransomware

Sigrun is a file-locking ransomware that demands ransom in Dash or Bitcoin for file decryption

Sigrun is a ransomware virus that was discovered by security researchers in the middle of May 2018.^[1] Malware enters machine unnoticed, executes its payload and then locks up all audio, video, picture, text, database and other personal files. It uses complicated cryptography to add a .sigrun file extension, making all data unusable.

The virus drops ransom note into each of the “RESTORE-SIGRUN.txt” into each of the infected folders and also opens up a browser tab with the same message in .html format. Users are asked to contact hackers via sigrun_decryptor@protonmail.ch in order to get their files back. Victims are asked to pay up to $2,500 in Dash or Bitcoin cryptocurrency, although Russians can get a decryptor for free.

It is interesting how ransomware authors are going for Norse mythology as Sigrun means “victory rune” and is a valkyrie – a mythological angel-like creature. Nevertheless, the authors of the ransomware are of Russian origin due to the fact that they try to avoid infecting Russian individuals.

The file-locking virus spreads via contaminated attachments in spam emails. Users who open the .txt, .pdf, .doc, .zip, or other affixed files instantaneously download malware into their computers. It is then ready to start its malicious activities.

First, the crypto-virus modifies certain system files (including registry entries) to acquire boot persistence. This way, it can start up every time Windows is launched. Next, it initiates a full system scan to find files to lock up. As soon it is complete, Sigrun malware encrypts data and executes the ransom notes to inform the user about the situation. 

Various file types are targeted by the virus, including .txt, .doc, .html, .xlsx, .dat, .mp3, .jpg. .gif and similar. For example, the encoded file would look like this: picture.jpg.sigrun. The strong encryption algorithm is used for file encryption, and only a key can unlock them. These decryptors are usually stored on a remote server and are only accessible to hackers. Nevertheless, users should ignore the key – remove the ransomware first and then proceed with file recovery.

There are several files that the virus does not targets, including:

• .sigrun
• .admin
• .dll
• .sys
• .exe
• .ico
• .key, etc.

Users are urged to contact criminals via the sigrun_decryptor@protonmail.ch address. The size of ransom is unknown, and it seems like hackers communicate with the victim before agreeing on the size of the payment. It is typically demanded in Bitcoin or another popular cryptocurrency, like Monero or Ethereum. Victims are also offered the proof that decryption is possible – they can send authors three files which they would decode for free.

The note states the following:

Dear user, all your important files have been encrypted! Don't worry! Your files still can be restored by us! In order to restore it you need to contact with us via e-mail.

sigrun_decryptor@protonmail.ch

As a proof we will decrypt 3 files for free! Please, attach this to your message:

 As we already mentioned, cybercriminals should be ignored as they often do not provide the offered key. Besides, even if they do, they will know that you are susceptible to the demands and might contaminate your machine again in the future. Instead, reboot your PC in Safe Mode with Networking and take care of Sigrun removal. Security experts^[2] suggest using FortectIntego or SpyHunterCombo Cleaner for that task.

If you have a backup ready – you are lucky, as you can recover all your files without problems, as long as they are stored on a remote server and not connected to the contaminated machine. If you are not that prepared and didn't use data backup, you might be in a bit of trouble. However, you can always try third-party tools that may help you with file recovery.

Hackers help Russian victims for free

Russian cybercriminals are known to avoid infecting Russian-speaking individuals (including former USSR countries), as they are cautious of the authorities, who could target them if locals were involved.

When Sigrun is first executed, it checks for the keyboards layouts installed – “HKEY_CURRENT_USER\Keyboard Layout\Preload.” Once the virus finds the Russian layout, it does not encrypt files and merely deletes itself. However, not all former USSR countries use the Russian layout; therefore, those individuals can still get infected. Hackers also mentioned that they added a Ukrainian layout to the list of exceptions.

While authors of Sigrun virus ask for as much as $2,500 in Dash or Bitcoin for file decryption, all Russian-speaking users have to do is email culprits and they offer their help for free. 

Avoid deadly ransomware viruses by deleting spam emails

The best practice is not to contaminate your machine with viruses in the first place. Of course, there will never be a guarantee as malware authors continually modify their code to improve avoidance and develop their malicious software distribution methods. However, there is something you can do. You can be more careful and attentive while browsing the internet.

First of all, we suggest using strong passwords for each of your accounts and change them regularly. Note that unprotected RDP configuration or weak passwords might be an easy way for hackers to infiltrate your machine with malware.

Next, you should not open spam emails carelessly. Malicious attachments often hide inside these emails, as well as cleverly-disguised hyperlinks may lead you to malicious payload execution.

Therefore, if in doubt, make sure you delete the message even without looking at it. Beware that some criminals have decent social engineering skills^[3] and are great at luring people with perfectly constructed phishing emails.

Finally, avoid suspicious websites, especially cracked software and other file-sharing sites. Additionally, do not click on questionable ads as they might lead you to malware-ridden sites.

Sigrun virus elimination procedure

Remember, you have to remove Sigrun ransomware before you proceed with file recovery. Otherwise, your data will be contaminated and locked up again. If you have remote storage with a backup ready, do not connect it to your machine before you are sure that the virus is exterminated.

Malware can be eliminated using anti-malware tools that have the power to find the pieces of ransomware and other payload pieces. You need tools like SpyHunterCombo Cleaner or MalwarebytesMalwarebytes to fully eliminate the infection. Otherwise, you risk getting files affected again.

Ransomware viruses are serious threats and use sophisticated code. Thus, do not even try manual Sigrun removal as you will fail. Only trained professionals can execute that task. Instead, employ reputable security software, enter Safe Mode with Networking, and perform a full system scan. If you did not have a backup, check out the alternative file restoration methods below.