Elastic Defend high stable eql

Potential Remote Code Execution via Mail Server

This rule detects potential remote code execution attempts via commonly used mail server applications, by monitoring for unusual child processes and command line arguments.

View Source

Detection Logic

process where event.type == "start" and event.action == "exec" and process.parent.interactive == false and
(
  process.parent.name in ("exim4", "postfix", "smtpd", "sendmail", "dovecot", "amavisd-new", "amavisd", "spamd") or
  (
    process.parent.name == "master" and
    process.parent.executable like "/*/postfix*master"
  )
) and
not (
  (process.parent.name == "exim4" and process.args like "/usr/lib/nagios/plugins/check_file_age*") or
  (process.parent.name in ("amavisd-new", "amavisd") and process.command_line == "/usr/bin/gzip -d") or
  (process.parent.name == "dovecot" and process.command_line == "gzip") or
  (process.parent.name == "amavisd" and process.name == "amavisd")
) and
(
  process.name in (
    "scp", "gzip", "bzip2", "xz", "tar", "getcap", "capsh", "find", "nohup", "setsid", "timeout", "disown",
    "mkfifo", "printenv", "env", "chpasswd", "echo"
  ) or
  (
    process.name == "touch" and
    not process.args like (
      "/home/*/.esmtp_queue/*/lock", "/root/.esmtp_queue/*/lock", "/prod/prod/data/prodstage/possum/error/"
    )
  ) or
  process.name like ".*" or
  (
    process.name in ("whoami", "id", "hostname", "uname", "ps", "netstat", "ss", "ip", "ifconfig") and
    process.interactive == true and process.parent.interactive == false
  ) or
  process.executable like ("/dev/shm/*", "/tmp/*", "/var/tmp/*", "/root/*", "./*") or
  (
    process.executable like ("/bin/python*", "/usr/bin/python*", "/usr/local/bin/python*") and (
      process.args == "-c" or
      (
        process.args_count <= 2 and
        process.args like ("/tmp/*", "/var/tmp/*", "/dev/shm/*", "/var/www/*", "/root/*", "/home/*/*", "./*.py") and
        process.args like "*.py*"
      )
    ) and
    not process.args in ("--version", "app.py")
  ) or
  (
    process.executable like (
      "/bin/perl*", "/usr/bin/perl*", "/usr/local/bin/perl*",
      "/bin/ruby*", "/usr/bin/ruby*", "/usr/local/bin/ruby*",
      "/bin/lua*", "/usr/bin/lua*", "/usr/local/bin/lua*",
      "/bin/node", "/usr/bin/node", "/usr/local/bin/node"
    ) and
    (process.args like "-e*" or process.args_count <= 2)
  ) or
  (
    process.executable like ("/bin/php*", "/usr/bin/php*", "/usr/local/bin/php*") and
    (process.args like "-r*" or process.args_count <= 2) and
    not (
      process.args like "var_export*" or
      process.command_line in ("php -r echo get_current_user().PHP_EOL;", "php -r echo date('T');")
    ) 
  ) or
  (
    process.name in ("nc", "ncat", "netcat", "netcat.openbsd", "netcat.traditional", "nc.openbsd", "nc.traditional") and (
      process.command_line regex ".*[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}.*" or
      process.command_line like "*http*"
    ) and
    not process.args in ("localhost", "127.0.0.1", "-z", "-zv") 
  ) or
  (
    process.name == "socat" and
    process.command_line like~ ("*exec*", "*tty*", "*fork*", "*file*", "*open*") and
    process.command_line like~ ("*tcp*", "*udp*", "*openssl*")
  ) or
  (
    process.name == "openssl" and (
      process.command_line like ("*s_server*", "*s_client*") or
      (process.args == "enc" and process.args in ("-d", "-base64", "-a", "-A"))
    )
  ) or
  (
    process.name in ("curl", "wget") and process.args like~ ("-o", "--output*", "-o-") and (
      process.command_line regex ".*[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}.*" or
      process.command_line like "*http*"
    ) and
    process.command_line like ("* /tmp/*", "* /var/tmp/*", "* /dev/shm/*", "* /var/www/*", "* ~/*", "* /home/*", "* /run/*", "* /var/run/*")
  ) or
  (
    process.name in ("base64", "basez", "base64plain", "base64url", "base64mime", "base64pem", "basenc", "base32", "base16") and
    process.args like~ "-*d*"
  ) or
  (
    process.name == "xxd" and process.args like~ ("-*r*", "-*p*")
  ) or
  (process.name == "sudo" and process.args == "-l") or
  (
    process.executable like ("/bin/chmod", "/usr/bin/chmod", "/usr/local/bin/chmod") and
    process.args like ("+x", "a+x", "0777", "755", "777", "+s", "u+s", "g+s")
  ) or
  (
    process.executable like ("/bin/cat", "/usr/bin/cat", "/usr/local/bin/cat") and
    process.args like (
      "/etc/passwd", "/etc/shadow", "/etc/hostname", "/etc/hosts", "*ssh*", "/proc/self/environ",
      "*.env*", "*../../../*", "*/secrets/kubernetes.io/serviceaccount/*", "*/.docker/config.json*",
      "*/.npmrc*", "*.aws/credentials*", "*/.aws/config*"
    )
  ) or
  (
    process.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish", "busybox") and
    process.args in ("-c", "-cl", "-lc") and (
      process.command_line like (
        /* Suspicious Paths */
        "* /tmp/* ", "* /var/tmp/* ", "* /dev/shm/*", "* /var/www/*", "* /run/*", "* /var/run/*",

        /* Interpreter Execution */
        "*python* -c*", "*php* -r*", "*perl* -e*", "*ruby* -e*", "*lua* -e*", "*node * -e *",

        /* Encoding, Decoding & Piping */
        "*
| sh", "*
| sh *", "*
| sh ", "*
| bash*", "*
| bash*", "*
| zsh*",  "*
| zsh*", "*
| dash*",  "*
| dash*",
        "*
| python*", "*
| python*", "*
| php*", "*
| php*", "*
| perl*", "*
| perl*", "*
| ruby*", "*
| ruby*",
        "*
| node*", "*
| node*", "*
| lua*",  "*
| lua*", "*
| busybox*", "*
| busybox*", "*
| *base64 -d*", "*
| *base64 --decode*",
        "*
| *base64 --decode*", "*
| *openssl base64 -d*", "*xxd *", "*
| openssl*enc * -d *", "*b64decode -r*",

        /* Reverse Shells */
        "*netcat *", "* nc *", "*ncat *", "*/dev/tcp*", "*/dev/udp/*", "*socat *", "*openssl*s_client *", "*stty*raw*-echo*",

        /* File Access */
        "*>*/etc/cron*", "*/etc/ssh*", "*/home/*/.ssh/*", "*/root/.ssh*", "*~/.ssh/*", "*/etc/shadow*", "*/etc/passwd*", "*chpasswd*",

        /* Helpers */
        "*nohup*", "*setsid *", "*timeout *sh -c *", "*disown*", "*env *sh *-c*",

        /* Miscellaneous */
        "*chattr *", "*busybox *",  "*#!*", "*chmod +x *", "*chmod 777*", 
        
        /* Decompression */
        "*gzip -*d *", "*bzip2 -*d *", "*xz -*d *", "*tar -*x*",
         
         /* Path Traversal */
         "*../../../*etc/*", "*/.../*", "*../../../*home/*/*", "*../../../*root/*"
      ) or
      (
        process.command_line like ("*wget *", "*curl *") and
        (
          process.command_line regex ".*[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}(:[0-9]{1,5})?/.*" or
          process.command_line like ("*http*", "*ftp*")
        ) and
        (
          (
            process.command_line regex~ """.*curl.* \-[a-zA-Z]*[oO]( .+
| \-.*)?""" or
            process.command_line like~ ("*curl* --output*", "*curl* --remote-name*")
          ) or
          (
            (
              process.command_line regex~ """.*wget.* \-[a-zA-Z]*O.*""" or
              process.command_line like~ "*wget* --output-document*"
            ) and
          not process.command_line like """*--output-document "-"*"""
          ) or
          process.command_line like ("*
| *sh*", "*
| *python*", "*
| *php*", "*
| *perl*", "*
| *ruby*", "*
| *node*", "*
| *lua*", "*
| *busybox*") or
          (
            process.command_line like ("*curl *>> /*", "*curl *>>/*", "*curl *> /*", "*curl *>/*", "*wget *>> /*", "*wget *>>/*", "*wget *> /*", "*wget *>/*") and
            not process.command_line like ("*> /dev/null*", "*>/dev/null*", "*curl*/etc/cobra/*/uploads/whatsapp/*")
          )
        ) and
        not process.command_line like ("*-O /dev/null*", "*-o /dev/null*")
      )
    )
  )
) and
not (
  process.executable like ("/tmp/newroot/*", "/opt/lxc/*", "/var/snap/lxd/*") or
  process.parent.command_line == "runc init" or
  process.command_line in ("pickup -l -t unix -u", "pickup -l -t unix -u -c") or
  (
    process.parent.executable == "/etc/init.d/postfix" and process.command_line == "/bin/echo -n postfix is running"
  ) or
  (
    process.parent.executable == "/usr/libexec/postfix/master" and
    process.command_line like (
      "/usr/bin/hostname", "ps -eo pid,args", "uname -m", "/usr/bin/perl -w /root/check_megaraid_sas",
      "gzip /prod/prod/data/prodstage/pos/save/*"
    )
  ) or
  (
    process.parent.executable == "/usr/sbin/dovecot" and
    process.command_line like "*/usr/local/cpanel/3rdparty/wp-toolkit/plib/vendor/wp-cli/wpt-wp-cli.php*"
  ) or
  (
    process.parent.executable in ("/usr/sbin/sendmail", "/etc/init.d/sendmail") and
    process.name == "touch"
  ) or
  process.entry_leader.executable == "/usr/local/qualys/cloud-agent/bin/qualys-cloud-agent" or
  (process.parent.executable == "/tmp/usr/sbin/sendmail" and process.executable like ("/tmp/usr/bin/*", "/tmp/bin/*"))
)

Field Validations

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