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SEKOIA_Rootkit_Win_Purplefox_360_Tct

Detects Purple Fox payloads used during end-2021 and 2022 campaigns based on characteristics shared by TrendMicro details.

MalwarePurplefoxSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2022-03-28
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detects Purple Fox payloads used during end-2021 and 2022 campaigns based on characteristics shared by TrendMicro details.

Associated malware family: Purplefox.

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

rootkit-win-purplefox-360-tct.yarDetection Rule License 1.1
rule SEKOIA_Rootkit_Win_Purplefox_360_Tct : FILE
{
	meta:
		description = "Detects Purple Fox payloads used during end-2021 and 2022 campaigns based on characteristics shared by TrendMicro details."
		author = "Sekoia.io"
		id = "e992d574-6a44-4bea-97e2-6d5579ce8d01"
		date = "2022-03-28"
		modified = "2024-12-19"
		reference = "https://www.trendmicro.com/en_us/research/22/c/purple-fox-uses-new-arrival-vector-and-improves-malware-arsenal.html"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/rootkit_win_purplefox_360_tct.yar#L1-L21"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "6b4ca65bc05ea1e8036140a62b94c8b75afe30a5e37cae9a5ae2a9c828cd6275"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$rar = "Rar!"
		$str0 = "svchost.txt"
		$str1 = "rundll3222.exe"
		$str2 = "ojbkcg.exe"

	condition:
		$rar at 0 and all of ( $str* ) and filesize > 800KB and filesize < 2800KB
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$rartext"Rar!"
$str0text"svchost.txt"
$str1text"rundll3222.exe"
$str2text"ojbkcg.exe"

Condition

$rar at 0 and all of ( $str* ) and filesize > 800KB and filesize < 2800KB

In plain words (Heuristic)

  • The file must be smaller than 2800KB (a cheap guard that skips large files).
  • The file must be larger than 800KB.
  • All patterns in ( $str* ) must match.
  • Pattern $rar must be found at offset 0.

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References

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: e992d574-6a44-4bea-97e2-6d5579ce8d01

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE

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