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SEKOIA_Apt_Kimsuky_Sharpext_Jsexfil_Strings

Detects the exfiltration JS code of SharpExt

APT / threat actorKimsukySEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2022-07-29
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detects the exfiltration JS code of SharpExt

Associated malware family: Kimsuky.

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

Summary generated from the rule's metadata and condition.

Rule source

apt-kimsuky-sharpext-jsexfil-strings.yarDetection Rule License 1.1
rule SEKOIA_Apt_Kimsuky_Sharpext_Jsexfil_Strings : FILE
{
	meta:
		description = "Detects the exfiltration JS code of SharpExt"
		author = "Sekoia.io"
		id = "c9ebd123-6450-4424-93d1-60322bd97bf6"
		date = "2022-07-29"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/apt_kimsuky_sharpext_jsexfil_strings.yar#L1-L18"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "37ea72b369baaced89f30f655901cc4a9d6a70d00cfca3b92a1015aca64d4e2c"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$ = "var req_url" ascii fullword
		$ = "var newReqId" ascii fullword
		$ = "chrome.tabs.query" ascii fullword
		$ = "payload.message.flags = new Object();" ascii fullword

	condition:
		all of them and filesize < 50KB
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$text"var req_url"ascii fullword
$text"var newReqId"ascii fullword
$text"chrome.tabs.query"ascii fullword
$text"payload.message.flags = new Object();"ascii fullword

Condition

all of them and filesize < 50KB

In plain words (Heuristic)

  • The file must be smaller than 50KB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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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: c9ebd123-6450-4424-93d1-60322bd97bf6

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE

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