Brute Force Invalid Logon

I have a site which is getting constant Brute Force Invalid Login errors in the logs from different IP addresses all over the world. How do I stop this happening?

As an example, most are identical apart from different IP addresses:

Module Brute Force
Type Notice
Description Invalid Login
Timestamp 2018-12-13 12:11:22
Host 145.17.133.54
User
URL http://mail.DOMAINNAMEREMOVED.com//xmlrpc.php
Login Source XMLRPC Authentication
Raw Details

Show Raw Details

id => 737
module => brute_force
type => notice
code => invalid-login
timestamp => 2018-12-13 12:11:22
init_timestamp => 2018-12-13 12:11:21
remote_ip => 145.17.133.54
user_id => [empty string]
url => http://mail.DOMAINNAMEREMOVED.com//xmlrpc.php
memory_current => 17601832
memory_peak => 18585936
data => Array
details => Array
source => xmlrpc
authentication_types => Array
0 => username_and_password
user => Object WP_Error
errors => Array
invalid_username => Array
0 => ERROR: Invalid username. Lost your password?
error_data => Array()
username => steve
user_id => [boolean] false
SERVER => Array
SERVER_SOFTWARE => LiteSpeed
REQUEST_URI => //xmlrpc.php
PATH => /bin:/usr/bin:/usr/local/bin
HTTP_ACCEPT => */*
HTTP_ACCEPT_ENCODING => gzip, deflate
CONTENT_LENGTH => 194
HTTP_HOST => mail.DOMAINNAMEREMOVED.com
HTTP_REFERER => http://www.google.com.hk
HTTP_USER_AGENT => Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.90 Safari/537.36
HTTP_X_FORWARDED_FOR => 145.17.133.54
DOCUMENT_ROOT => /home/FOLDERNAMEREMOVED/DOMAINNAMEREMOVED.com
REMOTE_ADDR => 145.17.133.54
REMOTE_PORT => 46570
SERVER_ADDR => 77.72.4.98
SERVER_NAME => mail.DOMAINNAMEREMOVED.com
SERVER_ADMIN => [email protected]
SERVER_PORT => 80
PROXY_REMOTE_ADDR => 111.118.150.193
SCRIPT_FILENAME => /home/FOLDERNAMEREMOVED/DOMAINNAMEREMOVED.com/xmlrpc.php
QUERY_STRING => [empty string]
SCRIPT_URI => http://mail.DOMAINNAMEREMOVED.com/xmlrpc.php
SCRIPT_URL => /xmlrpc.php
SCRIPT_NAME => /xmlrpc.php
SERVER_PROTOCOL => HTTP/1.1
REQUEST_METHOD => POST
X-LSCACHE => on
PHP_SELF => /xmlrpc.php
REQUEST_TIME_FLOAT => 1544703081.7144
REQUEST_TIME => 1544703081