S0641: Kobalos

Kobalos is a multi-platform backdoor that can be used against Linux, FreeBSD, and Solaris. Kobalos has been deployed against high profile targets, including high-performance computers, academic servers, an endpoint security vendor, and a large internet service provider; it has been found in Europe, North America, and Asia. Kobalos was first identified in late 2019.[1][2]

EnterpriseS0641MalwareObject v1.0ModifiedApr 25, 2025, 14:44 UTC (UTC+00:00)

S0641: Kobalos describes [Kobalos](https://attack.mitre.org/software/S0641) is a multi-platform backdoor that can be used against Linux, FreeBSD, and Solaris. [Kobalos](https://attack.mitre.org/software/S0641) has been deployed against high profile targets, including high-performance computers, academic servers, an endpoint security vendor, and a large internet service provider; it has been found in Europe, North America, and Asia. [Kobalos](https://attack.mitre.org/software/S0641) was first identified in late 2019.(Citation: ESET Kobalos ...

Executive priority

S0641: Kobalos is an official MITRE ATT&CK software. Glexia treats it as defensive behavior context for prioritizing monitoring, control validation, and response planning without using the object by itself as an attribution claim.

Technical view

Security teams should validate S0641: Kobalos by reviewing the official ATT&CK relationships, mapped tactics (the mapped ATT&CK tactic context), supported platforms (Linux), and available local telemetry before making detection or mitigation decisions.

Likely telemetry

Official ATT&CK relationships and object metadata
Network, endpoint, and security-tool telemetry

Detection direction

Validate whether S0641: Kobalos appears in your detection coverage and tabletop scenarios.
Use the object to align executive risk language with SOC, incident response, and detection engineering work.
Do not treat ATT&CK relationship context as attribution without corroborating evidence.

Mitigation priorities

Map the object to existing controls and identify missing telemetry or response ownership.
Prioritize mitigations that reduce exposure on the listed platforms and tactics.
Review adjacent ATT&CK relationships before changing policy, detections, or reporting language.

Additional notes and limits

Baseline Glexia take generated from the official MITRE ATT&CK STIX object, source hash, tactics, platforms, and detection fields. It is safe to replace with a richer model-generated take for the same source hash later.

This baseline take is source-grounded and schema-validated, but it does not include environment-specific telemetry, incident evidence, or threat-intelligence corroboration.

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Official MITRE ATT&CK definition

Kobalos

View the same entry on attack.mitre.org (MITRE-hosted reference; in-page links above use the Glexia ATT&CK library.)

Glexia analysis

How security teams should use this page

Treat this object as behavior context, not an attribution claim. Validate the related groups, software, data sources, and mitigations against official ATT&CK relationships and your own telemetry before making control-coverage decisions.

ATT&CK relationship table

Techniques used

This mirrors the MITRE pattern of making group, software, campaign, and technique relationships scannable. Relationship notes come from mirrored ATT&CK relationship text when available.

Filter related techniques15 rows

Domain	ID	Name	Relationship / procedure
Enterprise	T1059.004	Unix ShellSub-technique	Kobalos can spawn a new pseudo-terminal and execute arbitrary commands at the command prompt.[1]
Enterprise	T1554	Compromise Host Software Binary	Kobalos replaced the SSH client with a trojanized SSH client to steal credentials on compromised systems.[2]
Enterprise	T1016	System Network Configuration Discovery	Kobalos can record the IP address of the target machine.[2]
Enterprise	T1070.003	Clear Command HistorySub-technique	Kobalos can remove all command history on compromised hosts.[1]
Enterprise	T1074	Data Staged	Kobalos can write captured SSH connection credentials to a file under the `/var/run` directory with a `.pid` extension for exfiltration.[2]
Enterprise	T1140	Deobfuscate/Decode Files or Information	Kobalos decrypts strings right after the initial communication, but before the authentication process.[2]
Enterprise	T1205	Traffic Signaling	Kobalos is triggered by an incoming TCP connection to a legitimate service from a specific source port.[1][2]
Enterprise	T1573.001	Symmetric CryptographySub-technique	Kobalos's post-authentication communication channel uses a 32-byte-long password with RC4 for inbound and outbound traffic.[1][2]
Enterprise	T1048	Exfiltration Over Alternative Protocol	Kobalos can exfiltrate credentials over the network via UDP.[2]
Enterprise	T1070.006	TimestompSub-technique	Kobalos can modify timestamps of replaced files, such as `ssh` with the added credential stealer or `sshd` used to deploy Kobalos.[2]
Enterprise	T1027	Obfuscated Files or Information	Kobalos encrypts all strings using RC4 and bundles all functionality into a single function call.[1]
Enterprise	T1056	Input Capture	Kobalos has used a compromised SSH client to capture the hostname, port, username and password used to establish an SSH connection from the compromised host.[1][2]
Enterprise	T1573.002	Asymmetric CryptographySub-technique	Kobalos's authentication and key exchange is performed using RSA-512.[1][2]
Enterprise	T1082	System Information Discovery	Kobalos can record the hostname and kernel version of the target machine.[2]
Enterprise	T1090.003	Multi-hop ProxySub-technique	Kobalos can chain together multiple compromised machines as proxies to reach their final targets.[1][2]

Relationship explorer

All related ATT&CK context

Change history

Object version and sync metadata

The fields below describe the current mirrored snapshot. When Glexia retains multiple ATT&CK source imports, you can open the table to compare the same object across releases (hashes and MITRE timestamps). For MITRE’s own release notes and roadmap, see ATT&CK resources — Updates.

ATT&CK release: 19.2
Object version: 1.0
Created: Aug 24, 2021, 18:56 UTC (UTC+00:00)
Modified: Apr 25, 2025, 14:44 UTC (UTC+00:00)
Raw hash: 66e5e9abab366190...

Imported snapshots across ATT&CK releases(2)

Release	Bundle imported	Object version	Modified	Status	Raw hash
19.2	Aug 6, 2026, 02:58 UTC (UTC+00:00)	1.0	Apr 25, 2025, 14:44 UTC (UTC+00:00)	Current bundle	`66e5e9abab36…`
19.1	Jul 14, 2026, 09:14 UTC (UTC+00:00)	1.0	Apr 25, 2025, 14:44 UTC (UTC+00:00)	Older bundle	`66e5e9abab36…`

Raw source

Mirrored ATT&CK source object

The raw object is retained through the mirrored ATT&CK source bundle and object hash. The raw endpoint returns the exact object from the mirrored bundle when available.

Open mirrored raw JSON Open MITRE-hosted copy

Source references

External references and citations

MITRE external references are preserved separately from Glexia analysis so citations remain traceable to their original source records.

[1]
ESET Kobalos Feb 2021
M.Leveille, M., Sanmillan, I. (2021, February 2). Kobalos – A complex Linux threat to high performance computing infrastructure. Retrieved August 24, 2021.
Open source URL
[2]
ESET Kobalos Jan 2021
M.Leveille, M., Sanmillan, I. (2021, January). A WILD KOBALOS APPEARS Tricksy Linux malware goes after HPCs. Retrieved August 24, 2021.
Open source URL
[3]
Kobalos
(Citation: ESET Kobalos Feb 2021)(Citation: ESET Kobalos Jan 2021)
[4]
mitre-attackS0641
Open source URL

Source and licensing

Source: MITRE ATT&CK®. © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. MITRE ATT&CK and ATT&CK are registered trademarks of The MITRE Corporation. Glexia is not affiliated with or endorsed by MITRE.

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