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YARA · Trellix Advanced Research Center

TRELLIX_ARC_MALW_Emotet

Rule to detect unpacked Emotet

MalwareEmotetTrellix Advanced Research CenterApache License 2.0Compiles with YARA-X
Author
Marc Rivero | McAfee ATR Team
Date
2020-07-21
Modified
2020-08-14
Score / Quality
75 / 70

What this rule detects

Rule to detect unpacked Emotet

Associated malware family: Emotet.

It defines 10 patterns (0 text, 10 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

malw-emotet.yarApache License 2.0
rule TRELLIX_ARC_MALW_Emotet : FINANCIAL FILE
{
	meta:
		description = "Rule to detect unpacked Emotet"
		author = "Marc Rivero | McAfee ATR Team"
		id = "5bc83065-dfdd-56b7-9983-200bff35c8b1"
		date = "2020-07-21"
		modified = "2020-08-14"
		reference = "https://github.com/advanced-threat-research/Yara-Rules/"
		source_url = "https://github.com/advanced-threat-research/Yara-Rules//blob/1919562a59f190bda60c982424f6a24c542ee3e0/malware/MALW_emotet.yar#L1-L32"
		license_url = "https://github.com/advanced-threat-research/Yara-Rules//blob/1919562a59f190bda60c982424f6a24c542ee3e0/LICENSE"
		hash = "a6621c093047446e0e8ae104769af93a5a8ed147ab8865afaafbbd22adbd052d"
		logic_hash = "223e4453a6c3b56b0bc0f91147fa55ea59582d64b8a5c08f1f8d06026044065e"
		score = 75
		quality = 70
		tags = "FINANCIAL, FILE"
		rule_version = "v1"
		malware_type = "financial"
		malware_family = "Backdoor:W32/Emotet"
		actor_type = "Cybercrime"
		actor_type = "Cybercrime"
		actor_group = "Unknown"

	strings:
		$pattern_0 = { 8b45fc 8be5 5d c3 55 8bec }
		$pattern_1 = { 3c39 7e13 3c61 7c04 3c7a 7e0b 3c41 }
		$pattern_2 = { 7c04 3c39 7e13 3c61 7c04 3c7a 7e0b }
		$pattern_3 = { 5f 8bc6 5e 5b 8be5 }
		$pattern_4 = { 5f 668906 5e 5b }
		$pattern_5 = { 3c30 7c04 3c39 7e13 3c61 7c04 }
		$pattern_6 = { 53 56 57 8bfa 8bf1 }
		$pattern_7 = { 3c39 7e13 3c61 7c04 3c7a 7e0b }
		$pattern_8 = { 55 8bec 83ec14 53 }
		$pattern_9 = { 5e 8be5 5d c3 55 8bec }

	condition:
		7 of them and filesize < 180224
}

Strings (10 patterns)

IdentifierTypeValueModifiers
$pattern_0hex{ 8b45fc 8be5 5d c3 55 8bec }
$pattern_1hex{ 3c39 7e13 3c61 7c04 3c7a 7e0b 3c41 }
$pattern_2hex{ 7c04 3c39 7e13 3c61 7c04 3c7a 7e0b }
$pattern_3hex{ 5f 8bc6 5e 5b 8be5 }
$pattern_4hex{ 5f 668906 5e 5b }
$pattern_5hex{ 3c30 7c04 3c39 7e13 3c61 7c04 }
$pattern_6hex{ 53 56 57 8bfa 8bf1 }
$pattern_7hex{ 3c39 7e13 3c61 7c04 3c7a 7e0b }
$pattern_8hex{ 55 8bec 83ec14 53 }
$pattern_9hex{ 5e 8be5 5d c3 55 8bec }

Condition

7 of them and filesize < 180224

In plain words (Heuristic)

  • The file must be smaller than 180224 (a cheap guard that skips large files).
  • At least 7 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).

  • a6621c093047446e0e8ae104769af93a5a8ed147ab8865afaafbbd22adbd052d

Licence & attribution

Author: Marc Rivero | McAfee ATR Team

Source repository: Trellix Advanced Research Center @ 1919562a59

Licence: Apache License 2.0 (repository licence)

Original rule

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

Rule id: 5bc83065-dfdd-56b7-9983-200bff35c8b1

Metadata

rule_versionv1
malware_typefinancial
malware_familyBackdoor:W32/Emotet
actor_typeCybercrime
actor_typeCybercrime
actor_groupUnknown

Tags:FINANCIALFILE

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