Sigma rule: Suspicious OpenSSH Daemon Error

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-ff934671c0fd, updated 2021-11-27T00:00:00.000Z.

Rule

Title: Suspicious OpenSSH Daemon Error
Status: test
Level: medium
Author: Florian Roth (Nextron Systems)
Date: 2017-06-30
Modified: 2021-11-27
File: rules/linux/builtin/sshd/lnx_sshd_susp_ssh.yml
Commit: ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects suspicious SSH / SSHD error messages that indicate a fatal or suspicious error that could be caused by exploiting attempts

Log source

product: linux
service: sshd

Detection

keywords:
    - 'unexpected internal error'
    - 'unknown or unsupported key type'
    - 'invalid certificate signing key'
    - 'invalid elliptic curve value'
    - 'incorrect signature'
    - 'error in libcrypto'
    - 'unexpected bytes remain after decoding'
    - 'fatal: buffer_get_string: bad string'
    - 'Local: crc32 compensation attack'
    - 'bad client public DH value'
    - 'Corrupted MAC on input'
condition: keywords

False positives (as the rule lists them)

Unknown

MITRE ATT&CK ids this rule names

T1190

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/linux/builtin/sshd/lnx_sshd_susp_ssh.yml

Sources and licences

SigmaHQ
"Suspicious OpenSSH Daemon Error" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/linux/builtin/sshd/lnx_sshd_susp_ssh.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License
Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Suspicious OpenSSH Daemon Error",
entity page, dataset version ref-ff934671c0fd, updated 2021-11-27T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/e76b413a-83d0-4b94-8e4c-85db4a5b8bdc (accessed 2026-11-03).
Underlying source: SigmaHQ rule e76b413a-83d0-4b94-8e4c-85db4a5b8bdc, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.