Solution:
If hacker attack on your wp-admin url then you can set password in wp-admin directory. Then you can avoid DDOS attack on your website.
Set password in wp-admin in apache.
htpasswd -c /etc/httpd/.htpasswd admin
Add below code in your .htaccess file
AuthName “Restricted Area”
AuthType Basic
AuthUserFile /etc/httpd/.htpasswd
AuthGroupFile /dev/null
require valid-user