new hack / malware script

got infected by this sh*t, all index.php files on my server, its added to header. it causes firefox to freeze up after some time and google reports your site as dangerous. not sure if its directly connected to wordpress as i run more sites on my server, but be careful. the date/time of files remains unchanged.

[Code moderated as per the Forum Rules. Please use the pastebin]

if you decode it you get

[Code moderated as per the Forum Rules. Please use the pastebin]

if u know more pls share the cause and solution to prevent this from happening