How to check backup on php shells?

Question

PHP

There is a site backup. Approximately 30 gigabytes of files.
How can I scan and check for the presence of a shell in folders and files?
There are suspicions that the previous administrator could leave this thing hidden in the depths of folders. What options are there to protect yourself when moving to another server?

Answer 1

Yes, there can be 1 line of code that can fucking demolish the entire site or give full access to an attacker.
If you are friends with php, then open each file and check, you can automate a superficial search, but then there will be no 99% guarantee, if you are not friends, then hire a programmer and they will do everything for you for $$$$$.
In order not to be unfounded, a simple code example (shell):
^^^
Add this line of code to some file (depending on the structure of the code), then just send a POST request to the desired page and voila ..
Given that THAT dude knows what's going on in your script and given that he had access to it, then trust me, there are a lot of different options for pestering you. What is the code above, you can just leave some field without filtering and use it to get information from the database or do something else

Answer 2

According to the request logs, when the site is deployed and running, identify suspicious activity. Then it's a matter of technology to track the entire chain.

Answer 3

https://yandex.ru/promo/manul/