WEBSHELL_ASP_Generic_Tiny
YARA detection rule by Arnim Rupp (https://github.com/ruppde) · Detection Rule License 1.1 https://github.com/Neo23x0/signature-base/blob/master/LICENSE
Generic tiny ASP webshell which uses any eval/exec function indirectly on user input or writes a file
rule EXT_WEBSHELL_PHP_Generic {
meta:
description = "php webshell having some kind of input and some kind of payload. restricted to small files or big ones including suspicious strings"
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 = 70
date = "2021-01-14"
modified = "2026-03-09"
hash = "bee1b76b1455105d4bfe2f45191071cf05e83a309ae9defcf759248ca9bceddd"
hash = "6bf351900a408120bee3fc6ea39905c6a35fe6efcf35d0a783ee92062e63a854"
hash = "e3b4e5ec29628791f836e15500f6fdea19beaf3e8d9981c50714656c50d3b365"
hash = "00813155bf7f5eb441e1619616a5f6b21ae31afc99caa000c4aafd54b46c3597"
hash = "e31788042d9cdeffcb279533b5a7359b3beb1144f39bacdd3acdef6e9b4aff25"
hash = "36b91575a08cf40d4782e5aebcec2894144f1e236a102edda2416bc75cbac8dd"
hash = "a34154af7c0d7157285cfa498734cfb77662edadb1a10892eb7f7e2fb5e2486c"
hash = "791a882af2cea0aa8b8379791b401bebc235296858266ddb7f881c8923b7ea61"
hash = "9a8ab3c225076a26309230d7eac7681f85b271d2db22bf5a190adbf66faca2e6"
hash = "0d3ee83adc9ebf8fb1a8c449eed5547ee5e67e9a416cce25592e80963198ae23"
hash = "3d8708609562a27634df5094713154d8ca784dbe89738e63951e12184ff07ad6"
hash = "70d64d987f0d9ab46514abcc868505d95dbf458387f858b0d7580e4ee8573786"
hash = "259b3828694b4d256764d7d01b0f0f36ca0526d5ee75e134c6a754d2ab0d1caa"
hash = "04d139b48d59fa2ef24fb9347b74fa317cb05bd8b7389aeb0a4d458c49ea7540"
hash = "58d0e2ff61301fe0c176b51430850239d3278c7caf56310d202e0cdbdde9ac3f"
hash = "731f36a08b0e63c63b3a2a457667dfc34aa7ff3a2aee24e60a8d16b83ad44ce2"
hash = "e4ffd4ec67762fe00bb8bd9fbff78cffefdb96c16fe7551b5505d319a90fa18f"
hash = "fa00ee25bfb3908808a7c6e8b2423c681d7c52de2deb30cbaea2ee09a635b7d4"
hash = "98c1937b9606b1e8e0eebcb116a784c9d2d3db0039b21c45cba399e86c92c2fa"
hash = "e9423ad8e51895db0e8422750c61ef4897b3be4292b36dba67d42de99e714bff"
hash = "7a16311a371f03b29d5220484e7ecbe841cfaead4e73c17aa6a9c23b5d94544d"
hash = "7ca5dec0515dd6f401cb5a52c313f41f5437fc43eb62ea4bcc415a14212d09e9"
hash = "3de8c04bfdb24185a07f198464fcdd56bb643e1d08199a26acee51435ff0a99f"
hash = "63297f8c1d4e88415bc094bc5546124c9ed8d57aca3a09e36ae18f5f054ad172"
hash = "a09dcf52da767815f29f66cb7b03f3d8c102da5cf7b69567928961c389eac11f"
hash = "d9ae762b011216e520ebe4b7abcac615c61318a8195601526cfa11bbc719a8f1"
hash = "dd5d8a9b4bb406e0b8f868165a1714fe54ffb18e621582210f96f6e5ae850b33"
id = "ce3c93a5-3088-5e7e-a0d4-8bea18cf9cc3"
strings:
$wfp_tiny1 = "escapeshellarg" fullword
$wfp_tiny2 = "addslashes" fullword
$gfp_tiny3 = "include \"./common.php\";" $gfp_tiny4 = "assert('FALSE');"
$gfp_tiny5 = "assert(false);"
$gfp_tiny6 = "assert(FALSE);"
$gfp_tiny7 = "assert('array_key_exists("
$gfp_tiny8 = "echo shell_exec($aspellcommand . ' 2>&1');"
$gfp_tiny9 = "throw new Exception('Could not find authentication source with id ' . $sourceId);"
$gfp_tiny10 = "return isset( $_POST[ $key ] ) ? $_POST[ $key ] : ( isset( $_REQUEST[ $key ] ) ? $_REQUEST[ $key ] : $default );"
$gfp_tiny11 = "; This is the recommended, PHP 4-style version of the php.ini-dist file"
$php_short = "<?" wide ascii
$no_xml1 = "<?xml version" nocase wide ascii
$no_xml2 = "<?xml-stylesheet" nocase wide ascii
$no_asp1 = "<%@LANGUAGE" nocase wide ascii
$no_asp2 = /<script language="(vb|jscript|c#)/ nocase wide ascii
$no_pdf = "<?xpacket"
$php_new1 = /<\?=[^?]/ wide ascii
$php_new2 = "<?php" nocase wide ascii
$php_new3 = "<script language=\"php" nocase wide ascii
$inp1 = "php://input" wide ascii
$inp2 = /_GET\s?\[/ wide ascii
$inp3 = /\(\s?\$_GET\s?\)/ wide ascii
$inp4 = /_POST\s?\[/ wide ascii
$inp5 = /\(\s?\$_POST\s?\)/ wide ascii
$inp6 = /_REQUEST\s?\[/ wide ascii
$inp7 = /\(\s?\$_REQUEST\s?\)/ wide ascii
$inp8 = /\(\s?\$_HEADERS\s?[\)\[]/ wide ascii
$inp15 = "_SERVER['HTTP_" wide ascii
$inp16 = "_SERVER[\"HTTP_" wide ascii
$inp17 = /getenv[\t ]{0,20}\([\t ]{0,20}['"]HTTP_/ wide ascii
$inp18 = "array_values($_SERVER)" wide ascii
$inp19 = /file_get_contents\("https?:\/\// wide ascii
$inp20 = "TSOP_" wide ascii
$cpayload1 = /\beval[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload2 = /\bexec[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload3 = /\bshell_exec[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload4 = /\bpassthru[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload5 = /\bsystem[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload6 = /\bpopen[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload7 = /\bproc_open[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload8 = /\bpcntl_exec[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload9 = /\bassert[\n\t ]{0,500}\([^)0]/ nocase wide ascii
$cpayload10 = /\bpreg_replace[\n\t ]{0,500}\([^\)]{1,100}\/[ismxADSUXju]{0,11}(e|\\x65)/ nocase wide ascii
$cpayload12 = /\bmb_ereg_replace[\t ]{0,500}\([^\)]{1,100}'e'/ nocase wide ascii
$cpayload13 = /\bmb_eregi_replace[\t ]{0,500}\([^\)]{1,100}'e'/ nocase wide ascii
$cpayload20 = /\bcreate_function[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload21 = /\bReflectionFunction[\n\t ]{0,500}(\([^)]|\/\*)/ nocase wide ascii
$cpayload22 = /fetchall\(PDO::FETCH_FUNC[\n\t ]{0,500}[,}\)]/ nocase wide ascii
$m_cpayload_preg_filter1 = /\bpreg_filter[\n\t ]{0,500}(\([^\)]|\/\*)/ nocase wide ascii
$m_cpayload_preg_filter2 = "'|.{0,500}|e'" nocase wide ascii
$gen_bit_sus1 = /:\s{0,20}eval}/ nocase wide ascii
$gen_bit_sus2 = /\.replace\(\/\w\/g/ nocase wide ascii
$gen_bit_sus6 = "self.delete"
$gen_bit_sus9 = "\"cmd /c" nocase
$gen_bit_sus10 = "\"cmd\"" nocase
$gen_bit_sus11 = "\"cmd.exe" nocase
$gen_bit_sus12 = "%comspec%" wide ascii
$gen_bit_sus13 = "%COMSPEC%" wide ascii
$gen_bit_sus18 = "Hklm.GetValueNames();" nocase
$gen_bit_sus19 = "http://schemas.microsoft.com/exchange/" wide ascii
$gen_bit_sus21 = "\"upload\"" wide ascii
$gen_bit_sus22 = "\"Upload\"" wide ascii
$gen_bit_sus23 = "UPLOAD" fullword wide ascii
$gen_bit_sus24 = "fileupload" wide ascii
$gen_bit_sus25 = "file_upload" wide ascii
$gen_bit_sus29 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" fullword wide ascii
$gen_bit_sus29b = "abcdefghijklmnopqrstuvwxyz234567" fullword wide ascii
$gen_bit_sus30 = "serv-u" wide ascii
$gen_bit_sus31 = "Serv-u" wide ascii
$gen_bit_sus32 = "Army" fullword wide ascii
$gen_bit_sus33 = /\$_(GET|POST|REQUEST)\["\w"\]/ fullword wide ascii
$gen_bit_sus34 = "Content-Transfer-Encoding: Binary" wide ascii
$gen_bit_sus35 = "crack" fullword wide ascii
$gen_bit_sus44 = "<pre>" wide ascii
$gen_bit_sus45 = "<PRE>" wide ascii
$gen_bit_sus46 = "shell_" wide ascii
$gen_bit_sus50 = "bypass" wide ascii
$gen_bit_sus52 = " ^ $" wide ascii
$gen_bit_sus53 = ".ssh/authorized_keys" wide ascii
$gen_bit_sus55 = /\w'\.'\w/ wide ascii
$gen_bit_sus56 = /\w\"\.\"\w/ wide ascii
$gen_bit_sus57 = "dumper" wide ascii
$gen_bit_sus59 = "'cmd'" wide ascii
$gen_bit_sus60 = "\"execute\"" wide ascii
$gen_bit_sus61 = "/bin/sh" wide ascii
$gen_bit_sus62 = "Cyber" wide ascii
$gen_bit_sus63 = "portscan" fullword wide ascii
$gen_bit_sus66 = "whoami" fullword wide ascii
$gen_bit_sus67 = "$password='" fullword wide ascii
$gen_bit_sus68 = "$password=\"" fullword wide ascii
$gen_bit_sus69 = "$cmd" fullword wide ascii
$gen_bit_sus70 = "\"?>\"." fullword wide ascii
$gen_bit_sus71 = "Hacking" fullword wide ascii
$gen_bit_sus72 = "hacking" fullword wide ascii
$gen_bit_sus73 = ".htpasswd" wide ascii
$gen_bit_sus74 = /\btouch\(\$[^,]{1,30},/ wide ascii
$gen_bit_sus75 = "uploaded" fullword wide ascii
$gen_much_sus7 = "Web Shell" nocase
$gen_much_sus8 = "WebShell" nocase
$gen_much_sus3 = "hidded shell"
$gen_much_sus4 = "WScript.Shell.1" nocase
$gen_much_sus5 = "AspExec"
$gen_much_sus14 = "\\pcAnywhere\\" nocase
$gen_much_sus15 = "antivirus" nocase
$gen_much_sus16 = "McAfee" nocase
$gen_much_sus17 = "nishang"
$gen_much_sus18 = "\"unsafe" fullword wide ascii
$gen_much_sus19 = "'unsafe" fullword wide ascii
$gen_much_sus24 = "exploit" fullword wide ascii
$gen_much_sus25 = "Exploit" fullword wide ascii
$gen_much_sus26 = "TVqQAAMAAA" wide ascii
$gen_much_sus30 = "Hacker" wide ascii
$gen_much_sus31 = "HACKED" fullword wide ascii
$gen_much_sus32 = "hacked" fullword wide ascii
$gen_much_sus33 = "hacker" wide ascii
$gen_much_sus34 = "grayhat" nocase wide ascii
$gen_much_sus35 = "Microsoft FrontPage" wide ascii
$gen_much_sus36 = "Rootkit" wide ascii
$gen_much_sus37 = "rootkit" wide ascii
$gen_much_sus38 = "/*-/*-*/" wide ascii
$gen_much_sus39 = "u\"+\"n\"+\"s" wide ascii
$gen_much_sus40 = "\"e\"+\"v" wide ascii
$gen_much_sus41 = "a\"+\"l\"" wide ascii
$gen_much_sus42 = "\"+\"(\"+\"" wide ascii
$gen_much_sus43 = "q\"+\"u\"" wide ascii
$gen_much_sus44 = "\"u\"+\"e" wide ascii
$gen_much_sus45 = "/*//*/" wide ascii
$gen_much_sus46 = "(\"/*/\"" wide ascii
$gen_much_sus47 = "eval(eval(" wide ascii
$gen_much_sus48 = "unlink(__FILE__)" wide ascii
$gen_much_sus49 = "Shell.Users" wide ascii
$gen_much_sus50 = "PasswordType=Regular" wide ascii
$gen_much_sus51 = "-Expire=0" wide ascii
$gen_much_sus60 = "_=$$_" wide ascii
$gen_much_sus62 = "++;$" wide ascii
$gen_much_sus63 = "++; $" wide ascii
$gen_much_sus64 = "_.=$_" wide ascii
$gen_much_sus70 = "-perm -04000" wide ascii
$gen_much_sus71 = "-perm -02000" wide ascii
$gen_much_sus72 = "grep -li password" wide ascii
$gen_much_sus73 = "-name config.inc.php" wide ascii
$gen_much_sus75 = "password crack" wide ascii
$gen_much_sus76 = "mysqlDll.dll" wide ascii
$gen_much_sus77 = "net user" wide ascii
$gen_much_sus80 = "fopen(\".htaccess\",\"w" wide ascii
$gen_much_sus81 = /strrev\(['"]/ wide ascii
$gen_much_sus82 = "PHPShell" fullword wide ascii
$gen_much_sus821 = "PHP Shell" fullword wide ascii
$gen_much_sus83 = "phpshell" fullword wide ascii
$gen_much_sus84 = "PHPshell" fullword wide ascii
$gen_much_sus87 = "deface" wide ascii
$gen_much_sus88 = "Deface" wide ascii
$gen_much_sus89 = "backdoor" wide ascii
$gen_much_sus90 = "r00t" fullword wide ascii
$gen_much_sus91 = "xp_cmdshell" fullword wide ascii
$gen_much_sus92 = "str_rot13" fullword wide ascii
$cmpayload1 = /\beval[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload2 = /\bexec[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload3 = /\bshell_exec[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload4 = /\bpassthru[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload5 = /\bsystem[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload6 = /\bpopen[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload7 = /\bproc_open[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload8 = /\bpcntl_exec[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload9 = /\bassert[\t ]{0,500}\([^)0]/ nocase wide ascii
$cmpayload10 = /\bpreg_replace[\t ]{0,500}\([^\)]{1,100}\/e/ nocase wide ascii
$cmpayload11 = /\bpreg_filter[\t ]{0,500}\([^\)]{1,100}\/e/ nocase wide ascii
$cmpayload12 = /\bmb_ereg_replace[\t ]{0,500}\([^\)]{1,100}'e'/ nocase wide ascii
$cmpayload20 = /\bcreate_function[\t ]{0,500}\([^)]/ nocase wide ascii
$cmpayload21 = /\bReflectionFunction[\t ]{0,500}\([^)]/ nocase wide ascii
$fp1 = "# Some examples from obfuscated malware:" ascii
$fp2 = "{@see TFileUpload} for further details." ascii
condition:
filesize < 500KB
and (
any of ($inp*)
)
and (
any of ($cpayload*) or
all of ($m_cpayload_preg_filter*)
)
and (
(
(
$php_short in (0..100) or
$php_short in (filesize - 1000..filesize)
)
and not any of ($no_*)
)
or any of ($php_new*)
)
and
((filesize < 1000 and not any of ($wfp_tiny*)) or
((
uint32be(0) == 0x47494638 or (
filesize < 4KB and
(
1 of ($gen_much_sus*) or
2 of ($gen_bit_sus*)
)
) or (
filesize < 20KB and
(
2 of ($gen_much_sus*) or
3 of ($gen_bit_sus*)
)
) or (
filesize < 50KB and
(
2 of ($gen_much_sus*) or
4 of ($gen_bit_sus*)
)
) or (
filesize < 100KB and
(
2 of ($gen_much_sus*) or
6 of ($gen_bit_sus*)
)
) or (
filesize < 150KB and
(
3 of ($gen_much_sus*) or
7 of ($gen_bit_sus*)
)
) or (
filesize < 500KB and
(
4 of ($gen_much_sus*) or
8 of ($gen_bit_sus*)
)
)
)
and
(filesize > 5KB or not any of ($wfp_tiny*))) or
(filesize < 500KB and (
4 of ($cmpayload*)
)
)
)
and not (
any of ($gfp_tiny*)
or 1 of ($fp*)
)
}