Whenever Apache2 web server returns error pages (such as – 404 not found, 403 access forbidden pages), it shows web server signature (like – Apache version number and operating system info) at the bottom of the pages.
Exposing web server signature with server info can be a security risk as you are unnecessarily telling attackers known vulnerabilities of your system. Thus it is recommended you disable all web server signatures as part of server hardening process.
To check your Server Signature is ON OR OFF via Online Service, visit http://seositecheckup.com/ It will show the details of your server signature.
If your server signature is OFF then it is fine. You have nothing to do with it. But if it is not, then place this below code at root .htaccess file. Save and upload it.
# Disable the server signature ServerSignature Off ServerTokens Prod