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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_WEBSHELL_JSP_Nov21_1

Detects JSP webshells

WebshellSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2021-11-23
Modified
2023-12-05
Score / Quality
70 / 85

What this rule detects

Detects JSP webshells

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
webshell-jsp-nov21-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_WEBSHELL_JSP_Nov21_1 : FILE
{
	meta:
		description = "Detects JSP webshells"
		author = "Florian Roth (Nextron Systems)"
		id = "117eed28-c44e-5983-b4c7-b555fc06d923"
		date = "2021-11-23"
		modified = "2023-12-05"
		reference = "https://www.ic3.gov/Media/News/2021/211117-2.pdf"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_spring4shell.yar#L2-L17"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "1dac7706421961c71ba6f8d7a223b80e4b77bf206bfb64ee18c7cc894b062a3c"
		score = 70
		quality = 85
		tags = "FILE"

	strings:
		$x1 = "request.getParameter(\"pwd\")" ascii
		$x2 = "excuteCmd(request.getParameter(" ascii
		$x3 = "getRuntime().exec (request.getParameter(" ascii
		$x4 = "private static final String PW = \"whoami\"" ascii

	condition:
		filesize < 400KB and 1 of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$x1text"request.getParameter(\"pwd\")"ascii
$x2text"excuteCmd(request.getParameter("ascii
$x3text"getRuntime().exec (request.getParameter("ascii
$x4text"private static final String PW = \"whoami\""ascii

Condition

filesize < 400KB and 1 of them

In plain words (Heuristic)

  • The file must be smaller than 400KB (a cheap guard that skips large files).
  • At least 1 patterns in the rule must match.

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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: 117eed28-c44e-5983-b4c7-b555fc06d923

Tags:FILE

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