Invasion problem in 2.0.3.1

every day i need to restore my index.php becouse some strange codes are inputed on it.
and a tmp folder is created on my opencart instalation
there is some thing that i can make for solve it?
or any one can help me to find the problem?

Contact your host, change all passwords. Ask them to do a scan for malwareSounds like someone has access to your server unbeknownst to you

i already did that , but they rold that cant find ho is acessing since they dont ofer support for third part software

Have you installed any modules lately >? you could turn check your FTP access on your cpanel ? to see if a user is uploading files.

look at your file manager and check if any files have been modified in the past few days or any new files been uploaded,

what code has been added to your index

my customer dont have ftp and cpanel acess