Technical minimum
Update core, plugins and themes, remove unused extensions, use strong passwords and limit administrative access.
Enable SSL, configure SMTP correctly and make sure backups include both files and the database.
Hosting layer
On Hostilla.pl, WordPress security is supported by exploit scanners, Imunify360, CXS, backups and Installatron automation for updates and backups.
During an infection, quick identification of files, modification dates and the vulnerability source matters.