YARA Detection Rule: WEBSHELL_ASP_Encoded
Repository: Neo23x0/signature-base
Detects: Webshell in VBscript or JScript encoded using *.Encode plus a suspicious string
Author: Arnim Rupp (https://github.com/ruppde)
Reference: Internal Research

Pattern signatures:
$encoded1 = "VBScript.Encode" nocase wide ascii
        $encoded2 = "JScript.Encode" nocase wide ascii
        $data1 = "#@~^" wide ascii
        $sus1 = "shell" nocase wide ascii
        $sus2 = "cmd" fullword wide ascii
        $sus3 = "password" fullword wide ascii
        $sus4 = "UserPass" fullword wide ascii

        //strings from private rule capa_asp
        $tagasp_short1 = /<%[^"]/ wide ascii
        // also looking for %> to reduce fp (yeah, short atom but seldom since special chars)
        $tagasp_short2 = "%>" wide ascii

        // classids for scripting host etc
        $tagasp_classid1 = "72C24DD5-D70A-438B-8A42-98424B88AFB8" nocase wide ascii
        $tagasp_classid2 = "F935DC22-1CF0-11D0-ADB9-00C04FD58A0B" nocase wide ascii
        $tagasp_classid3 = "093FF999-1EA0-4079-9525-9614C3504B74" nocase wide ascii
        $tagasp_classid4 = "F935DC26-1CF0-11D0-ADB9-00C04FD58A0B" nocase wide ascii
        $tagasp_classid5 = "0D43FE01-F093-11CF-8940-00A0C9054228" nocase wide 

Detection condition:
filesize < 500KB and (
        (
            any of ( $tagasp_long* ) or
            // TODO :  yara_push_private_rules.py doesn't do private rules in private rules yet
            any of ( $tagasp_classid* ) or
            (
                $tagasp_short1 and
                $tagasp_short2 in ( fil

Full rule:
rule WEBSHELL_ASP_Encoded
{
    meta:
        description = "Webshell in VBscript or JScript encoded using *.Encode plus a suspicious string"
        license = "Detection Rule License 1.1 https://github.com/Neo23x0/signature-base/blob/master/LICENSE"
        author = "Arnim Rupp (https://github.com/ruppde)"
        reference = "Internal Research"
        score = 75
        date = "2021/03/14"
        modified = "2023-07-05"
        hash = "1bc7327f9d3dbff488e5b0b69a1b39dcb99b3399"
        hash = "9885ee1952b5ad9f84176c9570ad4f0e32461c92"
        hash = "27a020c5bc0dbabe889f436271df129627b02196"
        hash = "f41f8c82b155c3110fc1325e82b9ee92b741028b"
        hash = "af40f4c36e3723236c59dc02f28a3efb047d67dd"

        id = "67c0e1f6-6da5-569c-ab61-8b[PII_REDACTED]"
    strings:
        $encoded1 = "VBScript.Encode" nocase wide ascii
        $encoded2 = "JScript.Encode" nocase wide ascii
        $data1 = "#@~^" wide ascii
        $sus1 = "shell" nocase wide ascii
        $sus2 = "cmd" fullword wide ascii
        $sus3 = "password" fullword wide ascii
        $sus4 = "UserPass" fullword wide ascii

        //strings from private rule capa_asp
        $tagasp_short1 = /<%[^"]/ wide ascii
        // also looking for %> to reduce fp (yeah, short atom but seldom since special chars)
        $tagasp_short2 = "%>" wide ascii

        // classids for scripting host etc
        $tagasp_classid1 = "72C24DD5-D70A-438B-8A42-98424B88AFB8" nocase wide ascii
        $tagasp_classid2 = "F935DC22-1CF0-11D0-ADB9-00C04FD58A0B" nocase wide ascii
        $tagasp_classid3 = "093FF999-1EA0-4079-9525-9614C3504B74" nocase wide ascii
        $tagasp_classid4 = "F935DC26-1CF0-11D0-ADB9-00C04FD58A0B" nocase wide ascii
        $tagasp_classid5 = "0D43FE01-F093-11CF-8940-00A0C9054228" nocase wide ascii
        $tagasp_long10 = "<%@ " wide ascii
        // <% eval
        $tagasp_long11 = /<% \w/ nocase wide ascii
        $tagasp_long12 = "<%ex" nocase wide ascii
        $tagasp_long13 = "<%ev" nocase