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T1021.004 SSH

Adversaries may use Valid Accounts to log into remote machines using Secure Shell (SSH). The adversary may then perform actions as the logged-on user.

SSH is a protocol that allows authorized users to open remote shells on other computers. Many Linux and macOS versions come with SSH installed by default, although typically disabled until the user enables it. On ESXi, SSH can be enabled either directly on the host (e.g., via vim-cmd hostsvc/enable_ssh) or via vCenter.421 The SSH server can be configured to use standard password authentication or public-private keypairs in lieu of or in addition to a password. In this authentication scenario, the user’s public key must be in a special file on the computer running the server that lists which keypairs are allowed to login as that user (i.e., SSH Authorized Keys).

Item Value
ID T1021.004
Sub-techniques T1021.001, T1021.002, T1021.003, T1021.004, T1021.005, T1021.006, T1021.007, T1021.008
Tactics TA0008
Platforms ESXi, Linux, macOS
Version 1.3
Created 11 February 2020
Last Modified 24 October 2025

Procedure Examples

ID Name Description
G0087 APT39 APT39 used secure shell (SSH) to move laterally among their targets.31
G1023 APT5 APT5 has used SSH for lateral movement in compromised environments including for enabling access to ESXi host servers.24
G0143 Aquatic Panda Aquatic Panda used SSH with captured user credentials to move laterally in victim environments.16
G0098 BlackTech BlackTech has used Putty for remote access.15
C0032 C0032 During the C0032 campaign, TEMP.Veles relied on encrypted SSH-based tunnels to transfer tools and for remote command/program execution.33
S0154 Cobalt Strike Cobalt Strike can SSH to a remote service.67
C0029 Cutting Edge During Cutting Edge, threat actors used SSH for lateral movement.32
S0363 Empire Empire contains modules for executing commands over SSH as well as in-memory VNC agent injection.5
G1016 FIN13 FIN13 has remotely accessed compromised environments via secure shell (SSH) for lateral movement.27
G0046 FIN7 FIN7 has used SSH to move laterally through victim environments.10
G0117 Fox Kitten Fox Kitten has used the PuTTY and Plink tools for lateral movement.18
G0036 GCMAN GCMAN uses Putty for lateral movement.17
G0119 Indrik Spider Indrik Spider has used SSH for lateral movement.29
S0599 Kinsing Kinsing has used SSH for lateral movement.9
G0032 Lazarus Group Lazarus Group used SSH and the PuTTy PSCP utility to gain access to a restricted segment of a compromised network.11
G0065 Leviathan Leviathan used ssh for internal reconnaissance.12
C0049 Leviathan Australian Intrusions Leviathan used SSH brute force techniques to move laterally within victim environments during Leviathan Australian Intrusions.34
G0045 menuPass menuPass has used Putty Secure Copy Client (PSCP) to transfer data.28
G0049 OilRig OilRig has used Putty to access compromised systems.23
S1187 reGeorg reGeorg can communicate using SSH through an HTTP tunnel.8
G0106 Rocke Rocke has spread its coinminer via SSH.30
G1045 Salt Typhoon Salt Typhoon has modified the loopback address on compromised switches and used them as the source of SSH connections to additional devices within the target environment, allowing them to bypass access control lists (ACLs).22
G1015 Scattered Spider Scattered Spider has used SSH to move laterally in victim environments and to access the vSphere vCenter Server GUI.1413
G1046 Storm-1811 Storm-1811 has used OpenSSH to establish an SSH tunnel to victims for persistent access.21
G0139 TeamTNT TeamTNT has used SSH to connect back to victim machines.20 TeamTNT has also used SSH to transfer tools and payloads onto victim hosts and execute them.19
G1048 UNC3886 UNC3886 has established remote SSH access to targeted ESXi hosts.2526

Mitigations

ID Mitigation Description
M1042 Disable or Remove Feature or Program Disable the SSH daemon on systems that do not require it, especially ESXi servers. For macOS, ensure Remote Login is disabled under Sharing Preferences.3
M1032 Multi-factor Authentication Require multi-factor authentication for SSH connections wherever possible, such as password protected SSH keys.
M1018 User Account Management Limit which user accounts are allowed to login via SSH.

References

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  2. Junestherry Dela Cruz. (2022, January 24). Analysis and Impact of LockBit Ransomware’s First Linux and VMware ESXi Variant. Retrieved March 26, 2025. ↩

  3. Sarah Edwards. (2020, April 30). Analysis of Apple Unified Logs: Quarantine Edition [Entry 6] – Working From Home? Remote Logins. Retrieved August 19, 2021. ↩

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  17. Kaspersky Lab’s Global Research & Analysis Team. (2016, February 8). APT-style bank robberies increase with Metel, GCMAN and Carbanak 2.0 attacks. Retrieved April 20, 2016. ↩

  18. CISA. (2020, September 15). Iran-Based Threat Actor Exploits VPN Vulnerabilities. Retrieved December 21, 2020. ↩

  19. Darin Smith. (2022, April 21). TeamTNT targeting AWS, Alibaba. Retrieved August 4, 2022. ↩

  20. Fishbein, N. (2020, September 8). Attackers Abusing Legitimate Cloud Monitoring Tools to Conduct Cyber Attacks. Retrieved September 22, 2021. ↩

  21. Microsoft Threat Intelligence. (2024, May 15). Threat actors misusing Quick Assist in social engineering attacks leading to ransomware. Retrieved March 14, 2025. ↩

  22. Cisco Talos. (2025, February 20). Weathering the storm: In the midst of a Typhoon. Retrieved February 24, 2025. ↩

  23. Unit42. (2016, May 1). Evasive Serpens Unit 42 Playbook Viewer. Retrieved February 6, 2023. ↩

  24. Perez, D. et al. (2021, May 27). Re-Checking Your Pulse: Updates on Chinese APT Actors Compromising Pulse Secure VPN Devices. Retrieved February 5, 2024. ↩

  25. Alexander Marvi, Brad Slaybaugh, Ron Craft, and Rufus Brown. (2023, June 13). VMware ESXi Zero-Day Used by Chinese Espionage Actor to Perform Privileged Guest Operations on Compromised Hypervisors. Retrieved March 26, 2025. ↩

  26. Marvi, A. et al.. (2023, March 16). Fortinet Zero-Day and Custom Malware Used by Suspected Chinese Actor in Espionage Operation. Retrieved March 22, 2023. ↩

  27. Ta, V., et al. (2022, August 8). FIN13: A Cybercriminal Threat Actor Focused on Mexico. Retrieved February 9, 2023. ↩

  28. PwC and BAE Systems. (2017, April). Operation Cloud Hopper. Retrieved April 5, 2017. ↩

  29. Mandiant Intelligence. (2022, June 2). To HADES and Back: UNC2165 Shifts to LOCKBIT to Evade Sanctions. Retrieved July 29, 2024. ↩

  30. Anomali Labs. (2019, March 15). Rocke Evolves Its Arsenal With a New Malware Family Written in Golang. Retrieved April 24, 2019. ↩

  31. Hawley et al. (2019, January 29). APT39: An Iranian Cyber Espionage Group Focused on Personal Information. Retrieved February 19, 2019. ↩

  32. Meltzer, M. et al. (2024, January 10). Active Exploitation of Two Zero-Day Vulnerabilities in Ivanti Connect Secure VPN. Retrieved February 27, 2024. ↩

  33. Miller, S, et al. (2019, April 10). TRITON Actor TTP Profile, Custom Attack Tools, Detections, and ATT&CK Mapping. Retrieved April 16, 2019. ↩

  34. CISA et al. (2024, July 8). People’s Republic of China (PRC) Ministry of State Security APT40 Tradecraft in Action. Retrieved February 3, 2025. ↩