webshell_php_generic

YARA detection rule by Arnim Rupp · https://creativecommons.org/licenses/by-nc/4.0/

php webshell having some kind of input and some kind of payload. restricted to small files or big ones inclusing suspicious strings

rule webshell_php_generic: WEBSHELL PROD {
  meta:
    description = "php webshell having some kind of input and some kind of payload. restricted to small files or big ones inclusing suspicious strings"
    license     = "https://creativecommons.org/licenses/by-nc/4.0/"
    author      = "Arnim Rupp"
    date        = "2021/01/14"
    hash        = "bee1b76b1455105d4bfe2f45191071cf05e83a309ae9defcf759248ca9bceddd"

  strings:
    $wfp_tiny1 = "escapeshellarg" fullword
    $wfp_tiny2 = "addslashes" fullword

  condition:
    not php_false_positive_tiny and
    capa_php_old_safe and
    capa_php_input and
    (capa_php_payload_evals or capa_php_payload_execs) and
    (
      (
        filesize < 1000 and
        not any of ($wfp_tiny*)
      ) or (
        capa_gen_sus and
        (
          filesize > 5KB or
          not any of ($wfp_tiny*)
        )
      ) or (
        filesize < 500KB and
        capa_php_payload_multiple
      )
    )
}

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

f38e2d0c-017c-441d-b260-c968e40f95c0

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

What does this mean?

Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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