Today, MalwareHunterTeam discovered a new variant of the CryptoMix ransomware that is appending the .x1881 extension to encrypted file names. It's has been about three weeks since a new CryptoMix variant was released, which is quite long for this family of ransomware.

This article will provide a brief summary of what has changed in this new variant. As we are always looking for weaknesses, if you are a victim of this variant and decide to pay the ransom, please send us the decryptor so we can take a look at it. You can also discuss or receive support for Cryptomix ransomware infections in our dedicated Cryptomix Help & Support Topic.

Changes in the x1881 Cryptomix Ransomware Variant

While the encryption methods stay the same in this variant, there have been some slight differences. The ransom note is still named _HELP_INSTRUCTION.TXT, but now uses the x1881@tuta.io, x1883@yandex.com, x1881@protonmail.com, x1884@yandex.com emails for a victim to contact for payment information.

x1881 CryptoMix Ransom Note
x1881  CryptoMix Ransom Note

The next noticeable change is the extension appended to encrypted files. With this version, when a file is encrypted by the ransomware, it will modify the filename and then append the .x1881 extension to encrypted file's name. For example, a test file encrypted by this variant has an encrypted file name of 0D0A516824060636C21EC8BC280FEA12.x1881.

Folder of Encrypted x1881 Files
Folder of Encrypted x1881 Files

This variant also contains 11 public RSA-1024 encryption keys that will be used to to encrypt the AES key used to encrypt a victim's files. This allows the ransomware to work completely offline with no network communication. This variant's 11 public RSA keys are the same as the previous Shark Cryptomix Ransomware variant.

As this is just a cursory analysis of this new variant, if anything else is discovered, we will be sure to update this article.

How to protect yourself from the x1881 CryptoMix Ransomware

In order to protect yourself from the x1881 variant of CryptoMix , or from any ransomware, it is important that you use good computing habits and security software. First and foremost, you should always have a reliable and tested backup of your data that can be restored in the case of an emergency, such as a ransomware attack.

You should also have security software that contains behavioral detections such as Emsisoft Anti-Malware or Malwarebytes.  Regardless of the security software you use, make sure it contains behavioral detections so you do not have to rely on signatures or heuristics.

Last, but not least, make sure you practice the following good online security habits, which in many cases are the most important steps of all:

  • Backup, Backup, Backup!
  • Do not open attachments if you do not know who sent them.
  • Do not open attachments until you confirm that the person actually sent you them,
  • Scan attachments with tools like VirusTotal.
  • Make sure all Windows updates are installed as soon as they come out! Also make sure you update all programs, especially Java, Flash, and Adobe Reader. Older programs contain security vulnerabilities that are commonly exploited by malware distributors. Therefore it is important to keep them updated.
  • Make sure you use have some sort of security software installed.
  • Use hard passwords and never reuse the same password at multiple sites.

For a complete guide on ransomware protection, you visit our How to Protect and Harden a Computer against Ransomware article.

IOCs

File Hashes:

SHA256: 8e6d55df373eb3b0d6e4e6d98cfc7a0dcba69a9443aa3b93c789c084604efd19

Filenames associated with the x1881 Cryptomix Variant:

_HELP_INSTRUCTION.TXT
C:\ProgramData\[random].exe

Registry entries associated with the x1881 CryptoMix Variant:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run "Admin"="C:\ProgramData\[Random].exe""

x1881 Ransom Note Text:

Hello!

Attention! All Your data was encrypted!

For specific informartion, please send us an email with Your ID number:

x1881@tuta.io

x1883@yandex.com

x1881@protonmail.com

x1884@yandex.com

Please send email to all email addresses! We will help You as soon as possible!


DECRYPT-ID-[id] number

Emails Associated with the x1881 Ransomware:

x1881@tuta.io
x1883@yandex.com
x1881@protonmail.com
x1884@yandex.com

Executed Commands:

sc stop VVS
sc stop wscsvc
sc stop WinDefend
sc stop wuauserv
sc stop BITS
sc stop ERSvc
sc stop WerSvc
cmd.exe /C bcdedit /set {default} recoveryenabled No
cmd.exe /C bcdedit /set {default} bootstatuspolicy ignoreallfailures
C:\Windows\System32\cmd.exe" /C vssadmin.exe Delete Shadows /All /Quiet

Bundled Public RSA-1024 Keys:

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCyagbOaf3s/ePCxre9cs9BwaX3 D40qF7jAzB/xoWktfDlY2PVslZ2reYhQC9dSIvkEtuZqlUUYgFUdaaqTsE7pA8ik 2zXI5Ou7I0YtwWRoFNCl8YlMTRKgDHRQhclPNbtpi2ucm507Unr8EnT2ZzcTOYv1 7ITFgkBdNr4zHLFrpQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDChVnFfbDa3rp1sug7tbE6ba/O RWAwsk6WQ21XHgAXF7dKuEtG/4q7QJyHahQvys2oLkJ4Et2+S4YS3FSYXYqNOq/e 5ahdS19KiuGLnf1u7acnsGvikJgvXiwe/NH2h48ZtK0Uyn1Q1ijVNU66f1pehSmB YQupamnC2XkV9d6Z0wIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDXbf7u6Pq5kB+O1Cb9GIG9GlVG Mswk342Er1HMiHFXUsVMlljLFTJPz5rdcVB4QAXsOynm67uw8yEAlNC90AHohuIV dGDNVoQuuyNvanI1Ur4cA4aKqpJZKbkVauTpCDdEAse4LSH4NrGTgCao42jiaksj pZvKyFK8yvdoAwd3JQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCetENrtjivjYOthpX2yTlYKJ0x gZ0R367J8tSFikEhVoko4SKRmN9Y1s88iCdeRPUZh2Q0rHOesf/AxONK1buzygXl BkE5X86I3EFUFbPjyOnIgEKFru728aLlwkslqYPIWS29DZUCboHzv1YWU8gtFkwL 5bUEB444se2UXi+pjwIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCQa9aSkupoA7jxeOhS/mbRvy4u H/hI6XbTsv+ilfj8v9XHBaptsExUvCDG3fXvDKxSLxa6HBXnemM3weUDS0njH9Sb MJjImRjQ+OambwAYaj/hnFM3TYWU4KhPPKWrsxHT1ReSo1i+G2bNxr2gyS2D606N xaN4LNmYw3PLL2omGQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCIiEAs1V5JBCLKmDy0Il6rfC4w pQm0s9224Yvxs5pRRic3IQwAJ6wWw0Nrl42LxiA88jggso2EZ05lAl9FIuCNvzCr PO2QOjRLT0w2bYEEneK+rQR9sexZSI90zYVjziI26muOG1M8neAHqWkPvZI1a1sd hG5MwboKBkPYbtXI1wIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC4ShCcW3W2gmG5HT/Vcrzf4HKi OXAmVWpTRkyqxkw/wU7Ax+A63Fgo5tV4psuxHcJUGYQv4B8+Ag+POHmE4a7Vd4Ra 7tVXBEoyl1ZKF8fFCAAaw6G/ALCL0LEQiTLaqQuIjNXRo7S4Mt/alOM18uMP/kEA mqnGDXEblePIsMUzkQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDOXllDk/itDr0oW7hxm01XLeEo pVCg63jWxr5ZEKMU3zmYPtIPGayJbOacU+pPf6t77IMR8ainmJXjAK1c0V07XJv2 UrRsQARYDGEnItYphiYI7t1AgXSPoUi8pvQJrpja3WpuFNmhsWE2lz5uEO7QeejG jSToXALGsvmgvGq5SQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCWeBww97UHcRLjztOKvXB0xzRC LcZGov/Y/6x/m8uo42nLkyPgUjrqR7EAzB6bbB6L6aOgCJb2WyffOaNN5df07gIV f1Ea8u/jMIr5uhR+pnFMNB0jQIqqU9/slURM+U7dFvELbli5HL+7Ac/EehJNjLNW bpB5dTPCSSpKFoeoxQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCIX+Ay2zjnnViZsCDCk/TS2wZV 85YVVWpAXzsu4wzJzo4Mux2PK5pW0+i6+O1KZLcu+d5xElKM0KgrmE8uY1xylA18 SMBHHhBNhJdYXIaARFNp1uRG+kR8IDgT3sDrSseTt//l2tn8oo5xxw6UHtsBqRwF KP3u+Vspd+gFRsTC5wIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCxsV6vYenwHV4noHlPuOL/Dc7b dcLDWzJCmCToF5wCnUdkeifop7s6Kuz4nujPWq+6/foz5od8GySTtKiZtoq3lcmI 04RMzKqvo1PkR4RzfXGBLVk6EqeCrueY86l8Gu71oiPois8jJV6VQ96IJuc0HNRb IVKuPQZRttC1CjuZHQIDAQAB
-----END PUBLIC KEY-----