CTIPilot
AI-generated · no human review · verify critical claims against the linked source. how it works →

MythicRatatoskr

malware · malware:mythicratatoskr single-source

Go backdoor documented by ESET on 2026-10-22 that joins the Yggdrasil mesh network through public peers and reaches a command server hosted inside it over HTTPS; deployed on 2025-07-17 at a Ukrainian grain logistics company after a UAC-0099 intrusion that ESET assesses with high confidence was handed off to Sandworm, which ran a Group Policy wiper attack on 2025-09-17, with ESET unable to say which group operated the backdoor (ESET Research, 2026-10-22).

Coverage
1
first 2026-10-23 → last 2026-10-23
Latest activity
2026-10-23
ESET: a backdoor reaches its C2 through the Yggdrasil mesh; Sandworm wiped the victim two months after…
Peak priority
notable
1 notable
Targets
transport
sectors: transport · regions: russia-cis
Sources cited
1
1 hosts

Defender insights

What each entry about MythicRatatoskr tells a defender to do, newest first.

2026-10-23NOTABLEESET: a backdoor reaches its C2 through the Yggdrasil mesh; Sandworm wiped the victim two months after UAC-0099 got in

Exposure · triage · detection

Story timeline

  1. 2026-10-23MythicRatatoskr: ESET documents a Go backdoor that hides its command server inside the Yggdrasil mesh network, and a UAC-0099 to Sandworm access handoff that ended in a Group Policy wiper attack on a Ukrainian grain logistics firm
    active-threatsESET: a backdoor reaches its C2 through the Yggdrasil mesh; Sandworm wiped the victim two months after UAC-0099 got in
ATT&CK techniques (15 across 11 tactics)

15 techniques observed across 1 entry about this entity, derived from entry metadata and body evidence, never asserted without a published entry behind it · pinned to MITRE ATT&CK v20.0 · compare on the matrix · Navigator layer (JSON)

  • Initial AccessPhishing: Spearphishing Attachment
  • ExecutionScheduled Task/Job: Scheduled Task · Command and Scripting Interpreter: PowerShell
  • PersistenceScheduled Task/Job: Scheduled Task · Create or Modify System Process: Windows Service
  • Privilege EscalationScheduled Task/Job: Scheduled Task · Domain or Tenant Policy Modification: Group Policy Modification · Create or Modify System Process: Windows Service
  • StealthDelay Execution
  • Defense ImpairmentDomain or Tenant Policy Modification: Group Policy Modification
  • Lateral MovementLateral Tool Transfer
  • CollectionScreen Capture
  • Command and ControlApplication Layer Protocol: Web Protocols · Proxy: Internal Proxy · Proxy: Multi-hop Proxy · Ingress Tool Transfer · Encrypted Channel
  • ExfiltrationExfiltration Over C2 Channel
  • ImpactData Destruction

Initial Access TA0001

T1566.001Phishing: Spearphishing Attachment×1

Adversaries may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems. Spearphishing attachment is a specific variant of spearphishing. Spearphishing attachment is different from other forms of spearphishing in that it employs the use of malware attached to an email. All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, adversaries attach a file to the spearphishing email and usually rely upon User Execution to gain execution. Spearphishing may also involve social engineering techniques, such as posing as a trusted source.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Execution TA0002

T1053.005Scheduled Task/Job: Scheduled Task×1

Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library and Windows Management Instrumentation (WMI) to create a scheduled task. Adversaries may also utilize the Powershell Cmdlet `Invoke-CimMethod`, which leverages WMI class `PS_ScheduledTask` to create a scheduled task via an XML path.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1059.001Command and Scripting Interpreter: PowerShell×1

Adversaries may abuse PowerShell commands and scripts for execution. PowerShell is a powerful interactive command-line interface and scripting environment included in the Windows operating system. PowerShell can also be installed on Linux and macOS. Adversaries can use PowerShell to perform a number of actions, including discovery of information and execution of code. Examples include the <code>Start-Process</code> cmdlet which can be used to run an executable and the <code>Invoke-Command</code> cmdlet which runs a command locally or on a remote computer (though administrator permissions are required to use PowerShell to connect to remote systems).

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Persistence TA0003

T1053.005Scheduled Task/Job: Scheduled Task×1

Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library and Windows Management Instrumentation (WMI) to create a scheduled task. Adversaries may also utilize the Powershell Cmdlet `Invoke-CimMethod`, which leverages WMI class `PS_ScheduledTask` to create a scheduled task via an XML path.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1543.003Create or Modify System Process: Windows Service×1

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Privilege Escalation TA0004

T1053.005Scheduled Task/Job: Scheduled Task×1

Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library and Windows Management Instrumentation (WMI) to create a scheduled task. Adversaries may also utilize the Powershell Cmdlet `Invoke-CimMethod`, which leverages WMI class `PS_ScheduledTask` to create a scheduled task via an XML path.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1484.001Domain or Tenant Policy Modification: Group Policy Modification×1

Adversaries may modify Group Policy Objects (GPOs) to subvert the intended discretionary access controls for a domain, usually with the intention of escalating privileges on the domain. Group policy allows for centralized management of user and computer settings in Active Directory (AD). GPOs are containers for group policy settings made up of files stored within a predictable network path `\<DOMAIN>\SYSVOL\<DOMAIN>\Policies\`.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1543.003Create or Modify System Process: Windows Service×1

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Stealth TA0005

T1678Delay Execution×1

Adversaries may employ various time-based methods to evade detection and analysis. These techniques often exploit system clocks, delays, or timing mechanisms to obscure malicious activity, blend in with benign activity, and avoid scrutiny. Adversaries can perform this behavior within virtualization/sandbox environments or natively on host systems.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Defense Impairment TA0112

T1484.001Domain or Tenant Policy Modification: Group Policy Modification×1

Adversaries may modify Group Policy Objects (GPOs) to subvert the intended discretionary access controls for a domain, usually with the intention of escalating privileges on the domain. Group policy allows for centralized management of user and computer settings in Active Directory (AD). GPOs are containers for group policy settings made up of files stored within a predictable network path `\<DOMAIN>\SYSVOL\<DOMAIN>\Policies\`.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Lateral Movement TA0008

T1570Lateral Tool Transfer×1

Adversaries may transfer tools or other files between systems in a compromised environment. Once brought into the victim environment (i.e., Ingress Tool Transfer) files may then be copied from one system to another to stage adversary tools or other files over the course of an operation.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Collection TA0009

T1113Screen Capture×1

Adversaries may attempt to take screen captures of the desktop to gather information over the course of an operation. Screen capturing functionality may be included as a feature of a remote access tool used in post-compromise operations. Taking a screenshot is also typically possible through native utilities or API calls, such as <code>CopyFromScreen</code>, <code>xwd</code>, or <code>screencapture</code>.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Command and Control TA0011

T1071.001Application Layer Protocol: Web Protocols×1

Adversaries may communicate using application layer protocols associated with web traffic to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1090.001Proxy: Internal Proxy×1

Adversaries may use an internal proxy to direct command and control traffic between two or more systems in a compromised environment. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap. Adversaries use internal proxies to manage command and control communications inside a compromised environment, to reduce the number of simultaneous outbound network connections, to provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between infected systems to avoid suspicion. Internal proxy connections may use common peer-to-peer (p2p) networking protocols, such as SMB, to better blend in with the environment.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1090.003Proxy: Multi-hop Proxy×1

Adversaries may chain together multiple proxies to disguise the source of malicious traffic. Typically, a defender will be able to identify the last proxy traffic traversed before it enters their network; the defender may or may not be able to identify any previous proxies before the last-hop proxy. This technique makes identifying the original source of the malicious traffic even more difficult by requiring the defender to trace malicious traffic through several proxies to identify its source.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1105Ingress Tool Transfer×1

Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command and control channel or through alternate protocols such as ftp. Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment (i.e. Lateral Tool Transfer).

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

T1573Encrypted Channel×1

Adversaries may employ an encryption algorithm to conceal command and control traffic rather than relying on any inherent protections provided by a communication protocol. Despite the use of a secure algorithm, these implementations may be vulnerable to reverse engineering if secret keys are encoded and/or generated within malware samples/configuration files.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Exfiltration TA0010

T1041Exfiltration Over C2 Channel×1

Adversaries may steal data by exfiltrating it over an existing command and control channel. Stolen data is encoded into the normal communications channel using the same protocol as command and control communications.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Impact TA0040

T1485Data Destruction×1

Adversaries may destroy data and files on specific systems or in large numbers on a network to interrupt availability to systems, services, and network resources. Data destruction is likely to render stored data irrecoverable by forensic techniques through overwriting files or data on local and remote drives. Common operating system file deletion commands such as <code>del</code> and <code>rm</code> often only remove pointers to files without wiping the contents of the files themselves, making the files recoverable by proper forensic methodology. This behavior is distinct from Disk Content Wipe and Disk Structure Wipe because individual files are destroyed rather than sections of a storage disk or the disk's logical structure.

Evidence: 2026-10-23/mythicratatoskr-yggdrasil-mesh-c2-uac-0099-sandworm-wiper · ATT&CK page ↗

Entries about MythicRatatoskr (1)

2026-10-23 · view entry permalink →

NOTABLENATOB2

MythicRatatoskr: ESET documents a Go backdoor that hides its command server inside the Yggdrasil mesh network, and a UAC-0099 to Sandworm access handoff that ended in a Group Policy wiper attack on a Ukrainian grain logistics firm

ESET reports that on 2025-07-16 UAC-0099 gained access to a Ukrainian grain logistics company through a spearphishing attachment: a scheduled task ran a PowerShell payload, the MATCHBOIL downloader deployed the MATCHWOK backdoor, and the next day a previously undocumented Go backdoor, MythicRatatoskr, arrived, which ESET ties to that chain with high confidence because of the timing (ESET Research, 2026-10-22). Further copies reached other machines through an OpenSSH SFTP server, and a SOCKS5 server appeared on some of them (ESET Research, 2026-10-22). About two months later, on 2025-09-17, the SDelete utility was deployed through Active Directory Group Policy, which ESET calls standard Sandworm tradecraft and assesses with high confidence as Sandworm after UAC-0099 handed off the access; ESET could not say which group operated MythicRatatoskr, and it sets the pair beside the earlier Gamaredon and Turla collaboration (ESET Research, 2026-10-22).

The backdoor is built on the user-space yggstack, so it needs no tunnel interface or privileges to join the Yggdrasil mesh, an encrypted IPv6 overlay in the 200::/7 range: it picks three peers at random from an embedded list of public peers and then speaks JSON over HTTPS on port 443 to a command server that has an address only inside the mesh, and some samples wait ten minutes before connecting (ESET Research, 2026-10-22). It runs as a Windows service with an updater-style name, and it exfiltrates files and screenshots over the mesh without staging them (ESET Research, 2026-10-22). ESET notes that hosting the command server in the mesh may prevent network security tools from detecting the outbound connections to it and that blocking the public peer addresses is a viable mitigation (ESET Research, 2026-10-22).

Triage: ESET notes that legitimate users adopt Yggdrasil for resilient connectivity, research and hobby networking, so a single mesh connection needs a business-owner check, while a mesh peer connection together with a service named like an updater is the stronger combination (ESET Research, 2026-10-22).

The data-wiping attack was executed by deploying the SDelete utility via Active Directory Group Policy

blocking the public peer addresses is a viable mitigation

ESET Research (WeLiveSecurity) 2026-10-22

Builds on: Talos: malware tells the analysing LLM to skip it; the text is plain and therefore detectable

threat23 Oct 03:40Zsingle-sourceOpen finding →

Co-occurring entities

Derived: referenced by the same focused operational entries (weekly summaries and report roundups don't count); ×N counts the shared entries.

Where this entity is cited

  • Threats1

Source distribution

  • welivesecurity.com1 (100%)