I have found out this file under magento/pub ( somehow it's uploaded, not by me ) and I believe this is kind of "hacking" because after a while, the website is usually down.

The name of the file is af2fab30cfa2.php and here's the content:

[{"Expires":1,"Discard":false,"Value":""}]

I have checked the pub folder permissions, changed all of the passwords, etc but this happens once in a year randomly. What do you suggest to prevent the issues?

Server is at AWS, Magento 2.4.7 with Porto Theme ( from ThemeForest )