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DITEKSHEN_INDICATOR_RTF_Embedded_Excel_Urldownloadtofile

Detects RTF documents that embed Excel documents for detection evation.

Suspicious / huntingditekSHen detectionBSD 2-Clause LicenseCompiles with YARA-X
Author
ditekSHen
Date
2020-11-06
Modified
2024-09-06
Score / Quality
75 / 75

What this rule detects

Detects RTF documents that embed Excel documents for detection evation.

It defines 15 patterns (13 text, 2 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
indicator-rtf-embedded-excel-urldownloadtofile.yarBSD 2-Clause License
rule DITEKSHEN_INDICATOR_RTF_Embedded_Excel_Urldownloadtofile : FILE
{
	meta:
		description = "Detects RTF documents that embed Excel documents for detection evation."
		author = "ditekSHen"
		id = "39b8723c-1755-5e2f-8fb2-cca5e9eef915"
		date = "2020-11-06"
		modified = "2024-09-06"
		reference = "https://github.com/ditekshen/detection"
		source_url = "https://github.com/ditekshen/detection/blob/e76c93dcdedff04076380ffc60ea54e45b313635/yara/indicator_office.yar#L814-L840"
		license_url = "https://github.com/ditekshen/detection/blob/e76c93dcdedff04076380ffc60ea54e45b313635/LICENSE.txt"
		logic_hash = "9416664683c249a9dc2b3d506d9dea7067a638cc4ee5ef7138e5b33a8fcd2b96"
		score = 75
		quality = 75
		tags = "FILE"

	strings:
		$clsid1 = "2008020000000000c000000000000046" ascii nocase
		$obj1 = "\\objhtml" ascii
		$obj2 = "\\objdata" ascii
		$obj3 = "\\objupdate" ascii
		$obj4 = "\\objemb" ascii
		$obj5 = "\\objautlink" ascii
		$obj6 = "\\objlink" ascii
		$ole1 = { d0 cf 11 e0 a1 b1 1a e1 }
		$ole2 = "d0cf11e0a1b11ae1" ascii nocase
		$ole3 = "64306366313165306131623131616531" ascii
		$ole4 = "640a300a630a660a310a310a650a300a610a310a620a310a310a610a650a31"
		$ole5 = { 64 30 63 66 [0-2] 31 31 65 30 61 31 62 31 31 61 65 31 }
		$ole6 = "D0cf11E" ascii nocase
		$s1 = "55524c446f776e6c6f6164546f46696c6541" ascii nocase
		$s2 = "55524c4d4f4e" ascii nocase

	condition:
		uint32( 0 ) == 0x74725c7b and ( 1 of ( $clsid* ) and 1 of ( $obj* ) and 1 of ( $ole* ) and 1 of ( $s* ) )
}

Strings (15 patterns)

IdentifierTypeValueModifiers
$clsid1text"2008020000000000c000000000000046"ascii nocase
$obj1text"\\objhtml"ascii
$obj2text"\\objdata"ascii
$obj3text"\\objupdate"ascii
$obj4text"\\objemb"ascii
$obj5text"\\objautlink"ascii
$obj6text"\\objlink"ascii
$ole1hex{ d0 cf 11 e0 a1 b1 1a e1 }
$ole2text"d0cf11e0a1b11ae1"ascii nocase
$ole3text"64306366313165306131623131616531"ascii
$ole4text"640a300a630a660a310a310a650a300a610a310a620a310a310a610a650a31"
$ole5hex{ 64 30 63 66 [0-2] 31 31 65 30 61 31 62 31 31 61 65 31 }
$ole6text"D0cf11E"ascii nocase
$s1text"55524c446f776e6c6f6164546f46696c6541"ascii nocase
$s2text"55524c4d4f4e"ascii nocase

Condition

uint32( 0 ) == 0x74725c7b and ( 1 of ( $clsid* ) and 1 of ( $obj* ) and 1 of ( $ole* ) and 1 of ( $s* ) )

In plain words (Heuristic)

  • The file must start with “{\rt” — an RTF document.
  • At least 1 patterns in ( $clsid* ) must match.
  • At least 1 patterns in ( $obj* ) must match.
  • At least 1 patterns in ( $ole* ) must match.
  • At least 1 patterns in ( $s* ) must match.

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References

Licence & attribution

Author: ditekSHen

Source repository: ditekSHen detection @ e76c93dcde

Licence: BSD 2-Clause License (repository licence)

Copyright notice: Copyright 2021 by ditekSHen (https://github.com/ditekshen/detection).

Original rule

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

Rule id: 39b8723c-1755-5e2f-8fb2-cca5e9eef915

Tags:FILE

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