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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_EXPL_Zoho_RCE_Fix_Lines_Dec21_1

Detects lines in log lines of Zoho products that indicate RCE fixes (silent removal of evidence)

ExploitSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2021-12-06
Modified
2023-12-05
Score / Quality
65 / 85

What this rule detects

Detects lines in log lines of Zoho products that indicate RCE fixes (silent removal of evidence)

It defines 6 patterns (6 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
expl-zoho-rce-fix-lines-dec21-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_EXPL_Zoho_RCE_Fix_Lines_Dec21_1 : FILE
{
	meta:
		description = "Detects lines in log lines of Zoho products that indicate RCE fixes (silent removal of evidence)"
		author = "Florian Roth (Nextron Systems)"
		id = "633287e3-a377-5b3c-8520-a7790168eff5"
		date = "2021-12-06"
		modified = "2023-12-05"
		reference = "https://twitter.com/cyb3rops/status/1467784104930385923"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_zoho_rcef_logs.yar#L2-L27"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "e6d9c3364da57c03a5e838f485deefabec2f3ec67d19a9017e564ba702a72d03"
		score = 65
		quality = 85
		tags = "FILE"

	strings:
		$s1 = "RCEF="
		$sa1 = "\"attackStatus\"\\:\"active\""
		$sa2 = "\"attackStatus\":\"active\""
		$sd1 = "deletedCount"
		$sd_fp1 = "\"deletedCount\"\\:0"
		$sd_fp2 = "\"deletedCount\":0"

	condition:
		filesize < 6MB and $s1 and ( 1 of ( $sa* ) or ( $sd1 and not 1 of ( $sd_fp* ) ) )
}

Strings (6 patterns)

IdentifierTypeValueModifiers
$s1text"RCEF="
$sa1text"\"attackStatus\"\\:\"active\""
$sa2text"\"attackStatus\":\"active\""
$sd1text"deletedCount"
$sd_fp1text"\"deletedCount\"\\:0"
$sd_fp2text"\"deletedCount\":0"

Condition

filesize < 6MB and $s1 and ( 1 of ( $sa* ) or ( $sd1 and not 1 of ( $sd_fp* ) ) )

In plain words (Heuristic)

  • The file must be smaller than 6MB (a cheap guard that skips large files).
  • At least 1 patterns in ( $sa* ) must match.
  • At least 1 patterns in ( $sd_fp* ) must match.
  • Pattern $s1 must be present.
  • Pattern $sd1 must be present.

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References

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: 633287e3-a377-5b3c-8520-a7790168eff5

Tags:FILE

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