Sigma Ransomware – Threat infiltration via attachments through email.

What is Sigma Ransomware?

Sigma ransomware is dangerous threat to the PC, once it gets installed on the system; it encrypts the personal documents, photos, videos and other files of the user. Sigma ransomware is distributed as a malware spam pretending to be an email response to the ‘gigs section’ posted on craigslist by the users.

This email contains a Word or a RTF document that is password protected which lures the user into thinking that this is a genuine reply to their entry on craigslist. Since it is password protected, the user believes that the sender has gone through the trouble to secure the document, and hence, the user opens the file.

The sigma ransomware is downloaded from a random website once this word or RTF file is opened and its content enabled. Once the Sigma ransomware infects your system it will encrypt all your files and mark them with encrypted key at the bottom of each file.

Threat Behavior

Sigma ransomware is a dangerous ransomware that is distributed as a malware spam email response to user’s entry on craigslist under the ‘gigs’ section. This malware response contains an attached Word file that is password protected to provide credibility to the sender.

Once the user opens the Word file, it prompts the user to enable the content of the document. Once the user enables the content of the word file it launches an embedded VBA script that downloads and installs the sigma ransomware on the system. The VBA script downloads a password protected RAR file, which gets extracted in the %TEMP% folder. It then executes the extracted svchost.exe file. This svchost.exe is the sigma ransomware executable file that will then start encrypting your system.

Once the sigma ransomware has encrypted the files on the system, these files will include a file marker at the bottom of each file which is an encrypted key. The folders of all the infected files contain a readme.txt or readme.html that displays the ransom note from Sigma ransomware. It also places these files on the desktop where it changes the wallpaper prompting the user to open these files for the ransom note. This ransom note instructs the user to connect to the sigma ransomware TOR website to pay for the two-part decryption key.

The sigma ransomware threatens the user to pay the money within seven days of the infection otherwise the price will be doubled. Generally, the hackers do not provide any decryption key and the user is scammed out of their hard earned money. It is advised to never pay these cyber criminals because they can’t be trusted as they have already broken the user’s trust by infecting their PC with a ransomware.

Threat Summary

Name – Sigma Ransomware

Targeted Operating system – Windows XP, Windows Vista, Windows 7, Windows 8.0/8.1, Windows 10

Category – Ransomware

Symptoms – User’s files are encrypted and display encrypted key in the files. It changes the desktop wallpaper.

How to remove Sigma Ransomware from your system?

Sigma ransomware is a malicious program that is a dangerous threat to the system. It encrypts user data and demands money in return for the decryption key. It is advised that the user never pay these cyber criminals and follow ransomware removal guide to remove sigma ransomware from the system. The system should be updated with the latest anti-virus protection to keep it virus-free.

How did your system got infected?

The cybercriminals use various strategies for malware distribution which include –

1. Software Bundling: Software bundling is the process in which a malicious program is distributed with other free software, to get an unnoticed entry into your computer system. When a user installs a free application, the malicious programs gains a front door entry with the free application, the user has downloaded. Thus, it is a good idea to keep an eye on the installation screens while installing these free applications.
2. Infected Storage Devices: Your system can also get infected by using removable media such as USB hard drives and jump drives without scanning them with an anti-virus.
3. Spam Emails – Spamming is the most economic and common method used for the distribution of such malware. The targeted users get genuine looking emails which contain .doc, .txt, and other similar attachments. These attachments can be named as anything which can grab the user’s attention and triggers him/her to open the attachment. As soon as the user opens this attachment, the malware infects the user’s computer system.
4. Malicious Websites or Malevolent Advertisements: The malicious websites are the ones which are created just for promoting the malware infections. Such websites include but are not limited to porn sites, torrent sites and other free downloading platforms. By visiting such websites, the adware infects the user’s computer without permission. Fake advertisements and updates like Flash player and windows updates which ask the user to update to the latest version are a few examples. When the users click on such links, their computer system gets infected. That is why, it is highly recommended to resist clicking on such links. Also avoid clicking on advertisements offering free stuff such as Win an iPhones, cars or free overseas trips etc.

STEP A – Restore the encrypted data by Sigma Ransomware via Windows previous version.

If the system restore was enabled for both, system and user files, then you can recover your personal data through Windows Previous Version, provided the ransomware has not damaged the backup files. To restore your data follow the instructions given below –

1. Open My Computer and search for the folder you want to restore.
2. As soon as you find it, right click on it and choose the restore previous version option from the new window.
3. This option will display all the previous copies of the folder.
4. Now select restore data and through the options i.e. Open – Copy – Restore. 

To restart the system to Safe Mode with Networking,  if already switched ON then follow the below steps:

STEP B – Restart System using Safe mode with Networking

Tips to prevent your computer system from getting infected –

1. Keeping the Operating System Updated- In order to remain protected and avoid such infections, it is recommended to keep your Operating System updated by enabling the automatic update on your system. The systems with outdated or older versions of Operating System become an easy target for the attackers.
2. Resist clicking on spam emails – One of the major techniques used for malware distribution is forwarding spam emails to the user. The system gets infected as soon as the user clicks on the attachment. These mails appear to be genuine, so be aware and resist falling for these tricks.
3. Keep an eye on third party installations- It is quite important that you take due care while installing any third party applications for they are major source of such infections. Such malware programs come bundled with the free applications thereby requiring the user to remain cautious.
4. Regular periodical backup- In order to keep your data and files safe, it is recommended to take regular back up of all your data and files either on an external drive or cloud.
5. Use Anti-Virus Protection- We strongly recommend the use of antivirus protection/internet security in your PC like Bull Guard Internet Security and Sophos so that it remains safe.
6. Enable the Ad Blocker/Popup Blocker in your browser- Enabling the popup blocker/ ad blocker in your chosen browser will help you to stay protected from annoying adware.

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