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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_SUSP_Email_Suspicious_Onenote_Attachment_Jan23_2

Detects suspicious OneNote attachment that has a file name often used in phishing attacks

Suspicious / huntingSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X (with warnings)
Author
Florian Roth (Nextron Systems)
Date
2023-01-27
Modified
2023-12-05
Score / Quality
65 / 85

What this rule detects

Detects suspicious OneNote attachment that has a file name often used in phishing attacks

It defines 5 patterns (4 text, 1 hex, 0 regex).

YARA-X says: warning[text_as_hex]: hex pattern could be written as text literal

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
susp-email-suspicious-onenote-attachment-jan23-2.yarDetection Rule License 1.1
rule SIGNATURE_BASE_SUSP_Email_Suspicious_Onenote_Attachment_Jan23_2 : FILE
{
	meta:
		description = "Detects suspicious OneNote attachment that has a file name often used in phishing attacks"
		author = "Florian Roth (Nextron Systems)"
		id = "f8c58c73-2404-5ce6-8e8f-99b0dad84ad0"
		date = "2023-01-27"
		modified = "2023-12-05"
		reference = "Internal Research"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_onenote_phish.yar#L41-L61"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "eb6f992ce186022f04613af3bf4df629b00d85eac151f8bbd4b8ef96e6892eab"
		score = 65
		quality = 85
		tags = "FILE"

	strings:
		$hc1 = { 2E 6F 6E 65 22 0D 0A 0D 0A 35 46 4A 63 65 }
		$x01 = " attachment; filename=\"Invoice" nocase
		$x02 = " attachment; filename=\"ORDER" nocase
		$x03 = " attachment; filename=\"PURCHASE" nocase
		$x04 = " attachment; filename=\"SHIP" nocase

	condition:
		filesize < 5MB and $hc1 and 1 of ( $x* )
}

Strings (5 patterns)

IdentifierTypeValueModifiers
$hc1hex{ 2E 6F 6E 65 22 0D 0A 0D 0A 35 46 4A 63 65 }
$x01text" attachment; filename=\"Invoice"nocase
$x02text" attachment; filename=\"ORDER"nocase
$x03text" attachment; filename=\"PURCHASE"nocase
$x04text" attachment; filename=\"SHIP"nocase

Condition

filesize < 5MB and $hc1 and 1 of ( $x* )

In plain words (Heuristic)

  • The file must be smaller than 5MB (a cheap guard that skips large files).
  • At least 1 patterns in ( $x* ) must match.
  • Pattern $hc1 must be present.

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Licence & attribution

Author: Florian Roth (Nextron Systems)

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

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: f8c58c73-2404-5ce6-8e8f-99b0dad84ad0

Tags:FILE

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