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SEKOIA_Backdoor_Lin_Bifrost

Detect the Bifrost backdor based on strings

MalwareSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2024-03-05
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detect the Bifrost backdor based on strings

Targets: Linux ELF.

It defines 2 patterns (2 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

backdoor-lin-bifrost.yarDetection Rule License 1.1
rule SEKOIA_Backdoor_Lin_Bifrost : FILE
{
	meta:
		description = "Detect the Bifrost backdor based on strings"
		author = "Sekoia.io"
		id = "9726b5f5-8cc3-4fad-950b-f20cac04d496"
		date = "2024-03-05"
		modified = "2024-12-19"
		reference = "https://unit42.paloaltonetworks.com/new-linux-variant-bifrost-malware/"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/backdoor_lin_bifrost.yar#L1-L20"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		hash = "8e85cb6f2215999dc6823ea3982ff4376c2cbea53286e95ed00250a4a2fe4729"
		hash = "2aeb70f72e87a1957e3bc478e1982fe608429cad4580737abe58f6d78a626c05"
		hash = "f2bef6bed27f4b527118dd62b4035003c14afaffa72729c8117f213623f644ec"
		logic_hash = "a3fd671c02c29f67cf5b8d2d0e857336da72f989688f2db19cd028398080c5e2"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$ = "%c2%s%c3%u%c4%u-%.2u-%.2u %.2u:%.2u"
		$ = "%c1%s%c3D%c4%u-%.2u-%.2u %.2u:%.2u"

	condition:
		uint32be( 0 ) == 0x7f454c46 and all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$text"%c2%s%c3%u%c4%u-%.2u-%.2u %.2u:%.2u"
$text"%c1%s%c3D%c4%u-%.2u-%.2u %.2u:%.2u"

Condition

uint32be( 0 ) == 0x7f454c46 and all of them

In plain words (Heuristic)

  • The file must start with the ELF header — a Linux/Unix executable.
  • All patterns in the rule 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).

  • 8e85cb6f2215999dc6823ea3982ff4376c2cbea53286e95ed00250a4a2fe4729
  • 2aeb70f72e87a1957e3bc478e1982fe608429cad4580737abe58f6d78a626c05
  • f2bef6bed27f4b527118dd62b4035003c14afaffa72729c8117f213623f644ec

Licence & attribution

Author: Sekoia.io

Source repository: SEKOIA.IO Community @ a438a5901a

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: 9726b5f5-8cc3-4fad-950b-f20cac04d496

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE