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SIGNATURE_BASE_APT_SH_Esxi_Backdoor_Dec22

Detects malicious script found on ESXi servers

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth
Date
2022-12-14
Modified
2023-12-05
Score / Quality
75 / 85

What this rule detects

Detects malicious script found on ESXi servers

It defines 3 patterns (3 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
apt-sh-esxi-backdoor-dec22.yarDetection Rule License 1.1
rule SIGNATURE_BASE_APT_SH_Esxi_Backdoor_Dec22 : FILE
{
	meta:
		description = "Detects malicious script found on ESXi servers"
		author = "Florian Roth"
		id = "983ac20c-2e61-5365-8849-b3aeb999f909"
		date = "2022-12-14"
		modified = "2023-12-05"
		reference = "https://blogs.juniper.net/en-us/threat-research/a-custom-python-backdoor-for-vmware-esxi-servers"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/mal_ransom_esxi_attacks_feb23.yar#L73-L87"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "155a90a6c55b99285555634d91a66fca9c7e7297f05314fa4d6ce1d84257ee11"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$x1 = "mv /bin/hostd-probe.sh /bin/hostd-probe.sh.1" ascii fullword
		$x2 = "/bin/nohup /bin/python -u /store/packages/vmtools.py" ascii
		$x3 = "/bin/rm /bin/hostd-probe.sh.1"

	condition:
		filesize < 10KB and 1 of them
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$x1text"mv /bin/hostd-probe.sh /bin/hostd-probe.sh.1"ascii fullword
$x2text"/bin/nohup /bin/python -u /store/packages/vmtools.py"ascii
$x3text"/bin/rm /bin/hostd-probe.sh.1"

Condition

filesize < 10KB and 1 of them

In plain words (Heuristic)

  • The file must be smaller than 10KB (a cheap guard that skips large files).
  • At least 1 patterns in the rule must match.

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References

Licence & attribution

Author: Florian Roth

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 983ac20c-2e61-5365-8849-b3aeb999f909

Tags:FILE

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