How to change my Aws ec2-login password

Hi All

My Site was hacked. Actually I am working on Aws Server.

The site is working well and good. Past two days
when i open my site.

The chrome said.The Site contains Deceiptive Files. So when i open
my site files with winscp. I have found many unwanted php files
and images.

I have tried to delete the files with winscp. But i cant. So i try
to login through ssh and putty. But i cant login . It asks for
password. previously i did not set any password in ec2 login.

I think hacker or some one changed my password.

So how can i get the ec2-user password.

NOTE: I did not share my pem file with any one. How the unknown person or hacker uploaded the unwanted php files in my login

any one help me…

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