You work as a Penetration Tester for the Infosec Inc.

You work as a Penetration Tester for the Infosec Inc. Your company takes the projects of security auditing. Recently, your company has assigned you a project to test the security of the we-aresecure. com Website. The we-are-secure.com Web server is using Linux operating system. When you port scanned the we-are-secure.com Web server, you got that TCP port 23, 25, and 53 are open. When you tried to telnet to port 23, you got a blank screen in response. When you tried to type the dir, copy, date, del, etc. commands you got only blank spaces or underscores symbols on the screen. What may be the reason of such unwanted situation?