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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_RANSOM_COVID19_Apr20_1

Detects ransomware distributed in COVID-19 theme

MalwareSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2020-04-15
Modified
2023-12-05
Score / Quality
75 / 85

What this rule detects

Detects ransomware distributed in COVID-19 theme

Targets: Windows PE.

It defines 4 patterns (1 text, 3 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
mal-ransom-covid19-apr20-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_RANSOM_COVID19_Apr20_1 : FILE
{
	meta:
		description = "Detects ransomware distributed in COVID-19 theme"
		author = "Florian Roth (Nextron Systems)"
		id = "fc723d1f-e969-5af6-af57-70d00bf797f4"
		date = "2020-04-15"
		modified = "2023-12-05"
		reference = "https://unit42.paloaltonetworks.com/covid-19-themed-cyber-attacks-target-government-and-medical-organizations/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/crime_covid_ransom.yar#L2-L20"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "2779863a173ff975148cb3156ee593cb5719a0ab238ea7c9e0b0ca3b5a4a9326"
		logic_hash = "9b32ce1dff9d27c5f7541de97cd1198b0d837a69ee260b327c66a22ca6f30091"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$s1 = "/savekey.php" wide
		$op1 = { 3f ff ff ff ff ff 0b b4 }
		$op2 = { 60 2e 2e 2e af 34 34 34 b8 34 34 34 b8 34 34 34 }
		$op3 = { 1f 07 1a 37 85 05 05 36 83 05 05 36 83 05 05 34 }

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 700KB and 2 of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$s1text"/savekey.php"wide
$op1hex{ 3f ff ff ff ff ff 0b b4 }
$op2hex{ 60 2e 2e 2e af 34 34 34 b8 34 34 34 b8 34 34 34 }
$op3hex{ 1f 07 1a 37 85 05 05 36 83 05 05 36 83 05 05 34 }

Condition

uint16( 0 ) == 0x5a4d and filesize < 700KB and 2 of them

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • The file must be smaller than 700KB (a cheap guard that skips large files).
  • At least 2 patterns in the rule must match.

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References

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

  • 2779863a173ff975148cb3156ee593cb5719a0ab238ea7c9e0b0ca3b5a4a9326

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: fc723d1f-e969-5af6-af57-70d00bf797f4

Tags:FILE

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