Threat Explorer

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06 August 2014
30 August 2016
Also Known As:
Trojan.Synolocker [Symantec]
Infection Length:
Ransom.Synolocker is a Trojan horse that encrypts files on the compromised computer and then prompts the user to purchase a password in order to decrypt them.

Note: Ransom.Synolocker runs on Synology network-attached storage (NAS) devices.

For more information, see our blog:
The dawn of ransomwear: How ransomware could move to wearable devices

Note: Definitions prior to August, 2016 may detect this threat as Trojan.Synolocker

Antivirus Protection Dates

  • Initial Rapid Release version 07 August 2014 revision 019
  • Latest Rapid Release version 30 August 2016 revision 023
  • Initial Daily Certified version 07 August 2014 revision 009
  • Latest Daily Certified version 31 August 2016 revision 001
  • Initial Weekly Certified release date 13 August 2014
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
Ransom.Synolocker runs on Synology network-attached storage (NAS) devices.

When the Trojan is executed, it creates the following files:
  • /etc/synolock/
  • /etc/synolock/.decrypt
  • /etc/synolock/.restore
  • /etc/synolock/
  • /etc/synolock/synosync
  • /etc/synolock/
  • /etc/synolock/RSA_PUBLIC_KEY
  • /etc/synolock/RSA_PRIVATE_KEY
  • /usr/syno/synoman/redirect.html
  • /usr/syno/synoman/lock.png
  • /usr/syno/synoman/style.css
  • /usr/syno/synoman/synolockcode.txt
  • /usr/syno/synoman/crypted.log
  • /usr/syno/synoman/decrypted.log
  • /usr/syno/etc.defaults/rc.d/
  • /usr/syno/etc.defaults/rc.d/

It then modifies the following file:

Next, the Trojan searches for and encrypts files with the following extensions on the compromised NAS device:
  • .3fr
  • .7z
  • .accdb
  • .ai
  • .arw
  • .av
  • .bay
  • .bkf
  • .cdr
  • .cer
  • .cr
  • .dbf
  • .dcr
  • .ddrw
  • .der
  • .djvu
  • .dng
  • .do
  • .dwg
  • .dx
  • .eml
  • .eps
  • .erf
  • .gif
  • .gpg
  • .ico
  • .ind
  • .jp
  • .kd
  • .mbx
  • .md
  • .mef
  • .mp
  • .mrw
  • .nef
  • .nrw
  • .od
  • .orf
  • .p12
  • .p7b
  • .p7c
  • .pas
  • .pd
  • .pe
  • .pfx
  • .php
  • .pmg
  • .potx
  • .pp
  • .ps
  • .ptx
  • .r3d
  • .ra
  • .rtf
  • .rw
  • .sda
  • .sfx
  • .sld
  • .sql
  • .sr
  • .text
  • .wb2
  • .wp
  • .xl
  • .zip
  • wallet.

The Trojan then starts an HTTP server on port 80, which replaces the existing HTTP server used for device administration.

If the user attempts to open the administration Web page, the following message is displayed:
Automated Decryption Service. Copy and paste a valid RSA private key in the following form below.

If the correct RSA private key is entered the Trojan decrypts the files and removes itself from the compromised device.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Masaki Suenaga, Roberto Sponchioni