YARA · ESET malware-ioc

ESET_Apt_Windows_TA410_Flowcloud_Loader_Strings

Matches various strings found in TA410 FlowCloud first stage.

APT / threat actorESET malware-iocBSD 2-Clause LicenseCompiles with YARA-X

Author: ESET Research
Date: 2021-10-12
Modified: 2022-04-27
Score / Quality: 75 / 78

What this rule detects

Matches various strings found in TA410 FlowCloud first stage.

Targets: Windows PE.

It defines 22 patterns (22 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-windows-ta410-flowcloud-loader-strings.yarBSD 2-Clause License

rule ESET_Apt_Windows_TA410_Flowcloud_Loader_Strings : FILE
{
	meta:
		description = "Matches various strings found in TA410 FlowCloud first stage."
		author = "ESET Research"
		id = "a3fb894f-8e26-5cbd-a1f2-8a9ab1db0901"
		date = "2021-10-12"
		modified = "2022-04-27"
		reference = "https://github.com/eset/malware-ioc/"
		source_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/ta410/ta410.yar#L379-L415"
		license_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/LICENSE"
		logic_hash = "3c90723e009ffe2603910566ac52a324256676ee3ff128d94427681010e10e8b"
		score = 75
		quality = 78
		tags = "FILE"
		license = "BSD 2-Clause"
		version = "1"

	strings:
		$key = "y983nfdicu3j2dcn09wur9*^&initialize(y4r3inf;'fdskaf'SKF"
		$s2 = "startModule" fullword
		$s4 = "auto_start_module" wide
		$s5 = "load_main_module_after_install" wide
		$s6 = "terminate_if_fail" wide
		$s7 = "clear_run_mru" wide
		$s8 = "install_to_vista" wide
		$s9 = "load_ext_module" wide
		$s10 = "sll_only" wide
		$s11 = "fail_if_already_installed" wide
		$s12 = "clear_hardware_info" wide
		$s13 = "av_check" wide fullword
		$s14 = "check_rs" wide
		$s15 = "check_360" wide
		$s16 = "responsor.dat" wide ascii
		$s17 = "auto_start_after_install_check_anti" wide fullword
		$s18 = "auto_start_after_install" wide fullword
		$s19 = "extern_config.dat" wide fullword
		$s20 = "is_hhw" wide fullword
		$s21 = "SYSTEM\\Setup\\PrintResponsor" wide
		$event = "Global\\Event_{201a283f-e52b-450e-bf44-7dc436037e56}" wide ascii
		$s23 = "invalid encrypto hdr while decrypting"

	condition:
		uint16( 0 ) == 0x5a4d and ( $key or $event or 5 of ( $s* ) )
}

Strings (22 patterns)

Identifier	Type	Value	Modifiers
$key	text	"y983nfdicu3j2dcn09wur9*^&initialize(y4r3inf;'fdskaf'SKF"
$s2	text	"startModule"	fullword
$s4	text	"auto_start_module"	wide
$s5	text	"load_main_module_after_install"	wide
$s6	text	"terminate_if_fail"	wide
$s7	text	"clear_run_mru"	wide
$s8	text	"install_to_vista"	wide
$s9	text	"load_ext_module"	wide
$s10	text	"sll_only"	wide
$s11	text	"fail_if_already_installed"	wide
$s12	text	"clear_hardware_info"	wide
$s13	text	"av_check"	wide fullword
$s14	text	"check_rs"	wide
$s15	text	"check_360"	wide
$s16	text	"responsor.dat"	wide ascii
$s17	text	"auto_start_after_install_check_anti"	wide fullword
$s18	text	"auto_start_after_install"	wide fullword
$s19	text	"extern_config.dat"	wide fullword
$s20	text	"is_hhw"	wide fullword
$s21	text	"SYSTEM\\Setup\\PrintResponsor"	wide
$event	text	"Global\\Event_{201a283f-e52b-450e-bf44-7dc436037e56}"	wide ascii
$s23	text	"invalid encrypto hdr while decrypting"

Condition

uint16( 0 ) == 0x5a4d and ( $key or $event or 5 of ( $s* ) )

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
At least 5 patterns in ( $s* ) must match.
Pattern $key must be present.
Pattern $event must be present.

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References

https://github.com/eset/malware-ioc/

Licence & attribution

Author: ESET Research

Source repository: ESET malware-ioc @ 17baf44964

Licence: BSD 2-Clause License (stated in the rule's own meta)

“BSD 2-Clause”

Original rule

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

Rule id: a3fb894f-8e26-5cbd-a1f2-8a9ab1db0901

Metadata

version	1

Tags:FILE

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