Cybersecurity Advisory

New Sandworm Malware Cyclops Blink Replaces VPNFilter

Last Revised
Alert Code


The Sandworm actor, which the United Kingdom and the United States have previously attributed to the Russian GRU, has replaced the exposed VPNFilter malware with a new more advanced framework.

The United Kingdom's (UK) National Cyber Security Centre (NCSC), the Cybersecurity and Infrastructure Security Agency (CISA), the National Security Agency (NSA), and the Federal Bureau of Investigation (FBI) in the U.S. have identified that the actor known as Sandworm or Voodoo Bear is using a new malware, referred to here as Cyclops Blink. The NCSC, CISA, and the FBI have previously attributed the Sandworm actor to the Russian General Staff Main Intelligence Directorate’s Russian (GRU’s) Main Centre for Special Technologies (GTsST). The malicious cyber activity below has previously been attributed to Sandworm:

Cyclops Blink appears to be a replacement framework for the VPNFilter malware exposed in 2018, and which exploited network devices, primarily small office/home office (SOHO) routers and network attached storage (NAS) devices.

This advisory summarizes the VPNFilter malware it replaces, and provides more detail on Cyclops Blink, as well as the associated tactics, techniques and procedures (TTPs) used by Sandworm. An NCSC malware analysis report on Cyclops Blink is also available.

It also provides mitigation measures to help organizations defend against malware.

Click here for a PDF version of this report.

Technical Details


The malware was first exposed in 2018

A series of articles published by Cisco Talos in 2018 describes VPNFilter and its modules in detail. VPNFilter was deployed in stages, with most functionality in the third-stage modules. These modules enabled traffic manipulation, destruction of the infected host device, and likely enabled downstream devices to be exploited. They also allowed monitoring of Modbus SCADA protocols, which appears to be an ongoing requirement for Sandworm, as also seen in their previous attacks against ICS networks.

VPNFilter targeting was widespread and appeared indiscriminate, with some exceptions: Cisco Talos reported an increase of victims in Ukraine in May 2018. Sandworm also deployed VPNFilter against targets in the Republic of Korea before the 2018 Winter Olympics. 

In May 2018, Cisco Talos published the blog that exposed VPNFilter and the U.S. Department of Justice linked the activity to Sandworm and announced efforts to disrupt the botnet.

Activity since its exposure 

A Trendmicro blog in January 2021 detailed residual VPNFilter infections and provided data which showed that although there had been a reduction in requests to a known C2 domain, there was still more than a third of the original number of first-stage infections.

Sandworm has since shown limited interest in existing VPNFilter footholds, instead preferring to retool.

Cyclops Blink

Active since 2019

The NCSC, CISA, the FBI, and NSA, along with industry partners, have now identified a large-scale modular malware framework (T1129) which is targeting network devices. The new malware is referred to here as Cyclops Blink and has been deployed since at least June 2019, fourteen months after VPNFilter was disrupted. In common with VPNFilter, Cyclops Blink deployment also appears indiscriminate and widespread.

The actor has so far primarily deployed Cyclops Blink to WatchGuard devices, but it is likely that Sandworm would be capable of compiling the malware for other architectures and firmware.

Note: Note that only WatchGuard devices that were reconfigured from the manufacturer default settings to open remote management interfaces to external access could be infected

Malware overview 

The malware itself is sophisticated and modular with basic core functionality to beacon (T1132.002) device information back to a server and enable files to be downloaded and executed. There is also functionality to add new modules while the malware is running, which allows Sandworm to implement additional capability as required.

The NCSC has published a malware analysis report on Cyclops Blink which provides more detail about the malware.

Post exploitation 

Post exploitation, Cyclops Blink is generally deployed as part of a firmware ‘update’ (T1542.001). This achieves persistence when the device is rebooted and makes remediation harder.

Victim devices are organized into clusters and each deployment of Cyclops Blink has a list of command and control (C2) IP addresses and ports that it uses (T1008). All the known C2 IP addresses to date have been used by compromised WatchGuard firewall devices. Communications between Cyclops Blink clients and servers are protected under Transport Layer Security (TLS) (T1071.001), using individually generated keys and certificates. Sandworm manages Cyclops Blink by connecting to the C2 layer through the Tor network.


Cyclops Blink persists on reboot and throughout the legitimate firmware update process. Affected organizations should therefore take steps to remove the malware. 

WatchGuard has worked closely with the FBI, CISA, NSA and the NCSC, and has provided tooling and guidance to enable detection and removal of Cyclops Blink on WatchGuard devices through a non-standard upgrade process. Device owners should follow each step in these instructions to ensure that devices are patched to the latest version and that any infection is removed.

The tooling and guidance from WatchGuard can be found at:

In addition:

  • If your device is identified as infected with Cyclops Blink, you should assume that any passwords present on the device have been compromised and replace them (see NCSC password guidance for organizations.
  • You should ensure that the management interface of network devices is not exposed to the internet.

Indicators of Compromise

Please refer to the accompanying Cyclops Blink malware analysis report for indicators of compromise which may help detect this activity. 


This advisory has been compiled with respect to the MITRE ATT&CK® framework, a globally accessible knowledge base of adversary tactics and techniques based on real-world observations.




Initial Access


External Remote Services

The actors most likely deploy modified device firmware images by exploiting an externally available service



Command and Scripting Interpreter: Unix Shell

Cyclops Blink executes downloaded files using the Linux API



Pre-OS Boot: System Firmware

Cyclops Blink is deployed within a modified device firmware image


Boot or Logon Initialization Scripts: RC Scripts

Cyclops Blink is executed on device startup, using a modified RC script

Defense Evasion



Impair Defenses: Disable or Modify System Firewall

Cyclops Blink modifies the Linux system firewall to enable C2 communication




Masquerading: Match Legitimate Name or Location

Cyclops Blink masquerades as a Linux kernel thread process



System Information Discovery

Cyclops Blink regularly queries device information

Command and Control




Data Encoding: Non-Standard Encoding

Cyclops Blink command messages use a custom binary scheme to encode data


Fallback Channels

Cyclops Blink randomly selects a C2 server from contained lists of IPv4 addresses and port numbers


Application Layer Protocol: Web Protocols

Cyclops Blink can download files via HTTP or HTTPS


Encrypted Channel: Asymmetric Cryptography

Cyclops Blink C2 messages are individually encrypted using AES-256-CBC and sent underneath TLS


Non-Standard Port

The list of port numbers used by Cyclops Blink includes non-standard ports not typically associated with HTTP or HTTPS traffic



Exfiltration Over C2 Channel

Cyclops Blink can upload files to a C2 server

A Cyclops Blink infection does not mean that an organization is the primary target, but it may be selected to be, or its machines could be used to conduct attacks.

Organizations are advised to follow the mitigation advice in this advisory to defend against this activity, and to refer to indicators of compromise (not exhaustive) in the Cyclops Blink malware analysis report to detect possible activity on networks. 

UK organizations affected by the activity outlined in should report any suspected compromises to the NCSC at

Further Guidance

A variety of mitigations will be of use in defending against the malware featured in this advisory:

About This Document

This advisory is the result of a collaborative effort by United Kingdom’s National Cyber Security Centre (NCSC), the United States’ National Security Agency (NSA), the Federal Bureau of Investigation (FBI), and Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA). 

CISA, FBI, and NSA agree with this attribution and the details provided in the report.

This advisory has been compiled with respect to the MITRE ATT&CK® framework, a globally accessible knowledge base of adversary tactics and techniques based on real-world observations. 


This report draws on information derived from NCSC and industry sources. Any NCSC findings and recommendations made have not been provided with the intention of avoiding all risks and following the recommendations will not remove all such risk. Ownership of information risks remains with the relevant system owner at all times.

Disclaimer of Endorsement: The information and opinions contained in this document are provided "as is" and without any warranties or guarantees. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favoring by the United States Government, and this guidance shall not be used for advertising or product endorsement purposes.

For NSA client requirements or general cybersecurity inquiries, contact the Cybersecurity Requirements Center at 410-854-4200 or

Contact Information

To report suspicious or criminal activity related to information found in this joint Cybersecurity Advisory:

U.S. organizations contact your local FBI field office at, or the FBI’s 24/7 Cyber Watch (CyWatch) at (855) 292-3937 or by email at When available, please include the following information regarding the incident: date, time, and location of the incident; type of activity; number of people affected; type of equipment used for the activity; the name of the submitting company or organization; and a designated point of contact. To request incident response resources or technical assistance related to these threats, contact CISA at

Australian organizations should report incidents to the Australian Signals Directorate’s (ASD’s) ACSC via or call 1300 292 371 (1300 CYBER 1).

U.K. organizations should report a significant cyber security incident: (monitored 24 hrs) or for urgent assistance, call 03000 200 973.


February 23, 2022: Initial Version

This product is provided subject to this Notification and this Privacy & Use policy.