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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_LNX_Hunting_Linux_WHIRLPOOL_1

Hunting rule looking for strings observed in WHIRLPOOL samples.

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Mandiant
Date
2023-06-15
Modified
2023-12-05
Score / Quality
70 / 85

What this rule detects

Hunting rule looking for strings observed in WHIRLPOOL samples.

Targets: Linux ELF.

It defines 7 patterns (6 text, 1 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
apt-mal-lnx-hunting-linux-whirlpool-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_APT_MAL_LNX_Hunting_Linux_WHIRLPOOL_1 : FILE
{
	meta:
		description = "Hunting rule looking for strings observed in WHIRLPOOL samples."
		author = "Mandiant"
		id = "a997bd65-c502-53a0-8bb8-62daaa916f0d"
		date = "2023-06-15"
		modified = "2023-12-05"
		reference = "https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_barracuda_esg_unc4841_jun23.yar#L154-L173"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "177add288b289d43236d2dba33e65956"
		logic_hash = "d03c0e292b9b97bbf76585fc74208e4263d753807b8e4a445be80d41264d5432"
		score = 70
		quality = 85
		tags = "FILE"

	strings:
		$s1 = "error -1 exit" fullword
		$s2 = "create socket error: %s(error: %d)\n" fullword
		$s3 = "connect error: %s(error: %d)\n" fullword
		$s4 = {C7 00 20 32 3E 26 66 C7 40 04 31 00}
		$c1 = "plain_connect" fullword
		$c2 = "ssl_connect" fullword
		$c3 = "SSLShell.c" fullword

	condition:
		uint32( 0 ) == 0x464c457f and filesize < 15MB and ( all of ( $s* ) or all of ( $c* ) )
}

Strings (7 patterns)

IdentifierTypeValueModifiers
$s1text"error -1 exit"fullword
$s2text"create socket error: %s(error: %d)\n"fullword
$s3text"connect error: %s(error: %d)\n"fullword
$s4hex{C7 00 20 32 3E 26 66 C7 40 04 31 00}
$c1text"plain_connect"fullword
$c2text"ssl_connect"fullword
$c3text"SSLShell.c"fullword

Condition

uint32( 0 ) == 0x464c457f and filesize < 15MB and ( all of ( $s* ) or all of ( $c* ) )

In plain words (Heuristic)

  • The file must start with the ELF header — a Linux/Unix executable.
  • The file must be smaller than 15MB (a cheap guard that skips large files).
  • All patterns in ( $s* ) must match.
  • All patterns in ( $c* ) must match.

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References

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

  • 177add288b289d43236d2dba33e65956

Licence & attribution

Author: Mandiant

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: a997bd65-c502-53a0-8bb8-62daaa916f0d

Tags:FILE

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