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d9b7742 Jun 26, 2018
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@jvoisin @xarkes
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import "hash"
include "whitelist.yar"
/*
Detect:
- phpencode.org
- http://www.pipsomania.com/best_php_obfuscator.do
- http://atomiku.com/online-php-code-obfuscator/
- http://www.webtoolsvn.com/en-decode/
- http://obfuscator.uk/example/
- http://w3webtools.com/encode-php-online/
- http://www.joeswebtools.com/security/php-obfuscator/
- https://github.com/epinna/weevely3
- http://cipherdesign.co.uk/service/php-obfuscator
- http://sysadmin.cyklodev.com/online-php-obfuscator/
- http://mohssen.org/SpinObf.php
- https://code.google.com/p/carbylamine/
- https://github.com/tennc/webshell
- https://github.com/wireghoul/htshells
Thanks to:
- https://stackoverflow.com/questions/3115559/exploitable-php-functions
*/
global private rule IsPhp
{
strings:
$php = /<\?[^x]/
condition:
$php and filesize < 5MB
}
rule NonPrintableChars
{
strings:
/*
Searching only for non-printable characters completely kills the perf,
so we have to use atoms (https://gist.github.com/Neo23x0/e3d4e316d7441d9143c7)
to get an acceptable speed.
*/
$non_printables = /(function|return|base64_decode).{,256}[^\x09-\x0d\x20-\x7E]{3}/
condition:
(any of them) and not IsWhitelisted
}
rule PasswordProtection
{
strings:
$md5 = /md5\s*\(\s*\$_(GET|REQUEST|POST|COOKIE|SERVER)[^)]+\)\s*===?\s*['"][0-9a-f]{32}['"]/ nocase
$sha1 = /sha1\s*\(\s*\$_(GET|REQUEST|POST|COOKIE|SERVER)[^)]+\)\s*===?\s*['"][0-9a-f]{40}['"]/ nocase
condition:
(any of them) and not IsWhitelisted
}
rule ObfuscatedPhp
{
strings:
$eval = /(<\?php|[;{}])[ \t]*@?(eval|preg_replace|system|assert|passthru|(pcntl_)?exec|shell_exec|call_user_func(_array)?)\s*\(/ nocase // ;eval( <- this is dodgy
$eval_comment = /(eval|preg_replace|system|assert|passthru|(pcntl_)?exec|shell_exec|call_user_func(_array)?)\/\*[^\*]*\*\/\(/ nocase // eval/*lol*/( <- this is dodgy
$b374k = "'ev'.'al'"
$align = /(\$\w+=[^;]*)*;\$\w+=@?\$\w+\(/ //b374k
$weevely3 = /\$\w=\$[a-zA-Z]\('',\$\w\);\$\w\(\);/ // weevely3 launcher
$c99_launcher = /;\$\w+\(\$\w+(,\s?\$\w+)+\);/ // http://bartblaze.blogspot.fr/2015/03/c99shell-not-dead.html
$nano = /\$[a-z0-9-_]+\[[^]]+\]\(/ //https://github.com/UltimateHackers/nano
$ninja = /base64_decode[^;]+getallheaders/ //https://github.com/UltimateHackers/nano
$variable_variable = /\${\$[0-9a-zA-z]+}/
$too_many_chr = /(chr\([\d]+\)\.){8}/ // concatenation of more than eight `chr()`
$concat = /(\$[^\n\r]+\.){5}/ // concatenation of more than 5 words
$concat_with_spaces = /(\$[^\n\r]+\. ){5}/ // concatenation of more than 5 words, with spaces
$var_as_func = /\$_(GET|POST|COOKIE|REQUEST|SERVER)\s*\[[^\]]+\]\s*\(/
$comment = /\/\*([^*]|\*[^\/])*\*\/\s*\(/ // eval /* comment */ (php_code)
condition:
(any of them) and not IsWhitelisted
}
rule DodgyPhp
{
strings:
$basedir_bypass = /curl_init\s*\(\s*["']file:\/\// nocase
$basedir_bypass2 = "file:file:///" // https://www.intelligentexploit.com/view-details.html?id=8719
$disable_magic_quotes = /set_magic_quotes_runtime\s*\(\s*0/ nocase
$execution = /\b(eval|assert|passthru|exec|include|system|pcntl_exec|shell_exec|base64_decode|`|array_map|ob_start|call_user_func(_array)?)\s*\(\s*(base64_decode|php:\/\/input|str_rot13|gz(inflate|uncompress)|getenv|pack|\\?\$_(GET|REQUEST|POST|COOKIE|SERVER))/ nocase // function that takes a callback as 1st parameter
$execution2 = /\b(array_filter|array_reduce|array_walk(_recursive)?|array_walk|assert_options|uasort|uksort|usort|preg_replace_callback|iterator_apply)\s*\(\s*[^,]+,\s*(base64_decode|php:\/\/input|str_rot13|gz(inflate|uncompress)|getenv|pack|\\?\$_(GET|REQUEST|POST|COOKIE|SERVER))/ nocase // functions that takes a callback as 2nd parameter
$execution3 = /\b(array_(diff|intersect)_u(key|assoc)|array_udiff)\s*\(\s*([^,]+\s*,?)+\s*(base64_decode|php:\/\/input|str_rot13|gz(inflate|uncompress)|getenv|pack|\\?\$_(GET|REQUEST|POST|COOKIE|SERVER))\s*\[[^]]+\]\s*\)+\s*;/ nocase // functions that takes a callback as 2nd parameter
$htaccess = "SetHandler application/x-httpd-php"
$iis_com = /IIS:\/\/localhost\/w3svc/
$include = /include\s*\(\s*[^\.]+\.(png|jpg|gif|bmp)/ // Clever includes
$ini_get = /ini_(get|set|restore)\s*\(\s*['"](safe_mode|open_basedir|disable_(function|classe)s|safe_mode_exec_dir|safe_mode_include_dir|register_globals|allow_url_include)/ nocase
$pr = /(preg_replace(_callback)?|mb_ereg_replace|preg_filter)\s*\(.+(\/|\\x2f)(e|\\x65)['"]/ nocase // http://php.net/manual/en/function.preg-replace.php
$register_function = /register_[a-z]+_function\s*\(\s*['"]\s*(eval|assert|passthru|exec|include|system|shell_exec|`)/ // https://github.com/nbs-system/php-malware-finder/issues/41
$safemode_bypass = /\x00\/\.\.\/|LD_PRELOAD/
$shellshock = /\(\)\s*{\s*[a-z:]\s*;\s*}\s*;/
$udp_dos = /fsockopen\s*\(\s*['"]udp:\/\// nocase
$various = "<!--#exec cmd=" //http://www.w3.org/Jigsaw/Doc/User/SSI.html#exec
$at_eval = /@eval\s*\(/ nocase
$double_var = /\${\s*\${/
$extract = /extract\s*\(\s*\$_(GET|POST|REQUEST|COOKIE|SERVER)/
$reversed = /noitcnuf_etaerc|metsys|urhtssap|edulcni|etucexe_llehs/ nocase
$silenced_include =/@\s*include\s*/ nocase
condition:
(any of them) and not IsWhitelisted
}
rule DangerousPhp
{
strings:
$system = "system" fullword nocase // localroot bruteforcers have a lot of this
$ = "array_filter" fullword nocase
$ = "assert" fullword nocase
$ = "backticks" fullword nocase
$ = "call_user_func" fullword nocase
$ = "eval" fullword nocase
$ = "exec" fullword nocase
$ = "fpassthru" fullword nocase
$ = "fsockopen" fullword nocase
$ = "function_exists" fullword nocase
$ = "getmygid" fullword nocase
$ = "shmop_open" fullword nocase
$ = "mb_ereg_replace_callback" fullword nocase
$ = "passthru" fullword nocase
$ = /pcntl_(exec|fork)/ fullword nocase
$ = "php_uname" fullword nocase
$ = "phpinfo" fullword nocase
$ = "posix_geteuid" fullword nocase
$ = "posix_getgid" fullword nocase
$ = "posix_getpgid" fullword nocase
$ = "posix_getppid" fullword nocase
$ = "posix_getpwnam" fullword nocase
$ = "posix_getpwuid" fullword nocase
$ = "posix_getsid" fullword nocase
$ = "posix_getuid" fullword nocase
$ = "posix_kill" fullword nocase
$ = "posix_setegid" fullword nocase
$ = "posix_seteuid" fullword nocase
$ = "posix_setgid" fullword nocase
$ = "posix_setpgid" fullword nocase
$ = "posix_setsid" fullword nocase
$ = "posix_setsid" fullword nocase
$ = "posix_setuid" fullword nocase
$ = "preg_replace_callback" fullword
$ = "proc_open" fullword nocase
$ = "proc_close" fullword nocase
$ = "popen" fullword nocase
$ = "register_shutdown_function" fullword nocase
$ = "register_tick_function" fullword nocase
$ = "shell_exec" fullword nocase
$ = "shm_open" fullword nocase
$ = "show_source" fullword nocase
$ = "socket_create(AF_INET, SOCK_STREAM, SOL_TCP)" nocase
$ = "stream_socket_pair" nocase
$ = "suhosin.executor.func.blacklist" nocase
$ = "unregister_tick_function" fullword nocase
$ = "win32_create_service" fullword nocase
$ = "xmlrpc_decode" fullword nocase nocase
$ = /ob_start\s*\(\s*[^\)]/ //ob_start('assert'); echo $_REQUEST['pass']; ob_end_flush();
$whitelist = /escapeshellcmd|escapeshellarg/ nocase
condition:
(not $whitelist and (5 of them or #system > 250)) and not IsWhitelisted
}
rule HiddenInAFile
{
strings:
$gif = {47 49 46 38 ?? 61} // GIF8[version]a
$png = {89 50 4E 47 0D 0a 1a 0a} // \X89png\X0D\X0A\X1A\X0A
$jpeg = {FF D8 FF E0 ?? ?? 4A 46 49 46 } // https://raw.githubusercontent.com/corkami/pics/master/JPG.png
condition:
($gif at 0 or $png at 0 or $jpeg at 0) and (PasswordProtection or ObfuscatedPhp or DodgyPhp or DangerousPhp) and not IsWhitelisted
}
rule CloudFlareBypass
{
strings:
$ = "chk_jschl"
$ = "jschl_vc"
$ = "jschl_answer"
condition:
2 of them // Better be safe than sorry
}
private rule IRC
{
strings:
$ = "USER" fullword nocase
$ = "PASS" fullword nocase
$ = "PRIVMSG" fullword nocase
$ = "MODE" fullword nocase
$ = "PING" fullword nocase
$ = "PONG" fullword nocase
$ = "JOIN" fullword nocase
$ = "PART" fullword nocase
condition:
5 of them
}
private rule base64
{
strings:
$user_agent = "SFRUUF9VU0VSX0FHRU5UCg"
$eval = "ZXZhbCg"
$system = "c3lzdGVt"
$preg_replace = "cHJlZ19yZXBsYWNl"
$exec = "ZXhlYyg"
$base64_decode = "YmFzZTY0X2RlY29kZ"
$perl_shebang = "IyEvdXNyL2Jpbi9wZXJsCg"
$cmd_exe = "Y21kLmV4ZQ"
$powershell = "cG93ZXJzaGVsbC5leGU"
condition:
any of them
}
private rule hex
{
strings:
$globals = "\\x47\\x4c\\x4f\\x42\\x41\\x4c\\x53" nocase
$eval = "\\x65\\x76\\x61\\x6C\\x28" nocase
$exec = "\\x65\\x78\\x65\\x63" nocase
$system = "\\x73\\x79\\x73\\x74\\x65\\x6d" nocase
$preg_replace = "\\x70\\x72\\x65\\x67\\x5f\\x72\\x65\\x70\\x6c\\x61\\x63\\x65" nocase
$http_user_agent = "\\x48\\124\\x54\\120\\x5f\\125\\x53\\105\\x52\\137\\x41\\107\\x45\\116\\x54" nocase
$base64_decode = "\\x61\\x73\\x65\\x36\\x34\\x5f\\x64\\x65\\x63\\x6f\\x64\\x65\\x28\\x67\\x7a\\x69\\x6e\\x66\\x6c\\x61\\x74\\x65\\x28" nocase
condition:
any of them
}
private rule Hpack
{
strings:
$globals = "474c4f42414c53" nocase
$eval = "6576616C28" nocase
$exec = "65786563" nocase
$system = "73797374656d" nocase
$preg_replace = "707265675f7265706c616365" nocase
$base64_decode = "61736536345f6465636f646528677a696e666c61746528" nocase
condition:
any of them
}
private rule strrev
{
strings:
$globals = "slabolg" nocase fullword
$preg_replace = "ecalper_gerp" nocase fullword
$base64_decode = "edoced_46esab" nocase fullword
$gzinflate = "etalfnizg" nocase fullword
condition:
any of them
}
rule SuspiciousEncoding
{
condition:
(base64 or hex or strrev or Hpack) and not IsWhitelisted
}
rule DodgyStrings
{
strings:
$ = ".bash_history"
$ = /AddType\s+application\/x-httpd-(php|cgi)/ nocase
$ = /php_value\s*auto_prepend_file/ nocase
$ = /SecFilterEngine\s+Off/ nocase // disable modsec
$ = /Add(Handler|Type|OutputFilter)\s+[^\s]+\s+\.htaccess/ nocase
$ = ".mysql_history"
$ = ".ssh/authorized_keys"
$ = "/(.*)/e" // preg_replace code execution
$ = "/../../../"
$ = "/etc/passwd"
$ = "/etc/proftpd.conf"
$ = "/etc/resolv.conf"
$ = "/etc/shadow"
$ = "/etc/syslog.conf"
$ = "/proc/cpuinfo" fullword
$ = "/var/log/lastlog"
$ = "/windows/system32/"
$ = "LOAD DATA LOCAL INFILE" nocase
$ = "WScript.Shell"
$ = "WinExec"
$ = "b374k" fullword nocase
$ = "backdoor" fullword nocase
$ = /(c99|r57|fx29)shell/
$ = "cmd.exe" fullword nocase
$ = "powershell.exe" fullword nocase
$ = /defac(ed|er|ement|ing)/ fullword nocase
$ = "evilc0ders" fullword nocase
$ = "exploit" fullword nocase
$ = "find . -type f" fullword
$ = "hashcrack" nocase
$ = "id_rsa" fullword
$ = "ipconfig" fullword nocase
$ = "kernel32.dll" fullword nocase
$ = "kingdefacer" nocase
$ = "Wireghoul" nocase fullword
$ = "LD_PRELOAD" fullword
$ = "libpcprofile" // CVE-2010-3856 local root
$ = "locus7s" nocase
$ = "ls -la" fullword
$ = "meterpreter" fullword
$ = "nc -l" fullword
$ = "netstat -an" fullword
$ = "php://"
$ = "ps -aux" fullword
$ = "rootkit" fullword nocase
$ = "slowloris" fullword nocase
$ = "suhosin" fullword
$ = "sun-tzu" fullword nocase // Because quotes from the Art of War is mandatory for any cool webshell.
$ = /trojan (payload)?/
$ = "uname -a" fullword
$ = "visbot" nocase fullword
$ = "warez" fullword nocase
$ = "whoami" fullword
$ = /(r[e3]v[e3]rs[e3]|w[3e]b|cmd)\s*sh[e3]ll/ nocase
$ = /-perm -0[24]000/ // find setuid files
$ = /\/bin\/(ba)?sh/ fullword
$ = /hack(ing|er|ed)/ nocase
$ = /(safe_mode|open_basedir) bypass/ nocase
$ = /xp_(execresultset|regenumkeys|cmdshell|filelist)/
$vbs = /language\s*=\s*vbscript/ nocase
$asp = "scripting.filesystemobject" nocase
condition:
(IRC or 2 of them) and not IsWhitelisted
}
rule Websites
{
strings:
$ = "1337day.com" nocase
$ = "antichat.ru" nocase
$ = "b374k" nocase
$ = "ccteam.ru" nocase
$ = "crackfor" nocase
$ = "darkc0de" nocase
$ = "egyspider.eu" nocase
$ = "exploit-db.com" nocase
$ = "fopo.com.ar" nocase /* Free Online Php Obfuscator */
$ = "hashchecker.com" nocase
$ = "hashkiller.com" nocase
$ = "md5crack.com" nocase
$ = "md5decrypter.com" nocase
$ = "milw0rm.com" nocase
$ = "milw00rm.com" nocase
$ = "packetstormsecurity" nocase
$ = "pentestmonkey.net" nocase
$ = "phpjiami.com" nocase
$ = "rapid7.com" nocase
$ = "securityfocus" nocase
$ = "shodan.io" nocase
$ = "github.com/b374k/b374k" nocase
$ = "mumaasp.com" nocase
condition:
(any of them) and not IsWhitelisted
}