@posafoundation if you are on shared hosting you may want to think about moving to another trusted host. Some shared hosting platforms do not block other sites from accessing other sites. Although rare, it does happen.
Next thing would be to make sure you you have everything updated and cleaned out. If there is not update for a plugin, you may want to contact the author. Plugins not updated are plugins that can cause wide open gaps in security.
If you are sure your site was cleaned and everything was updated and you still was hacked, there is a vulnerable theme or plugin or the hosting platform is simply not secure. Attacking a bank for whatever reason sound a but involved and the server itself may have been compromised.