What software protection methods can a freelancer use in case of fraud on the part of the customer?

Question

PHP

I'm talking about backdoor scripts. Something like deleting a database or at least demolishing the current directory. To remotely execute it and use it as a defense of your interests.

Answer 1

Made a website. OK.
thrown into the cloud. Set up a domain and you're done.
The customer enjoys it.
Waiting for payment. As soon as the funds are received, you give the cloud to the customer.
Otherwise, just close the site.
I've been doing this for 6 years now. Everyone is happy and you always have the code before payment.
If comrades have gathered here who give the finished site to the customer before payment, it’s sad.
PS
All financial affairs must be carried out in writing.
Otherwise, I know you - I will offer to make a website for 100k, you give it to me and I send you.
No transaction confirmation

Answer 2

Use third-party services.. like a guarantor or prepayment.
Or 50/50..

Answer 3

And if the customer knows how to make backups, how will the demolition of the current directory help?
I somehow observed a conflict between the customer and the contractor, the contractor did not receive the money, deleted the work, and the customer restored everything from the backup ten minutes later and took away access.

Answer 4

Well, ladies, you can make a hole, and the customer will leave a negative review for you and write you leave holes and no one will ever order anything from you, you will have to change your account. And he will say that he paid for everything, and you ask for more, for example.
And if the customer is a programmer himself))