Security Question Re Allowing Remote Access

[cj911]

Hi Sorry if this is a stupid question but I'm a complete beginer to all this. With a steep learning curve lying ahead (does my head in having to try to learn where to learn before I can even begin to learn).

When someone gets remote access to install vicidial or to work on an existing installation they then have the IP Address username:root and password:vicidialnow what then stops that person(s) from accessing the server at will in the future?
Anyone who reads the install instructions knows the username and password does this not then mean that anyone who knows the IP Address where there is an instance of a vicidailnow installation can access the server with the username and password.
Also when box is booted the screen shows the username and password. I read in another post how to edit this. I used the command as stated in the other post and was simply going to delete part of the welcome message "Welcome to VICIDIALNOW!!!" In attempting this I logged in from home (serverbox in Office) using SSH Client & port 2442. The command (can't remember of the top of head what it was:if,is,iv,vi,pico or something like that, sorry been playing about with loads of them) resulted in the same information that it presented after login being displayed on screen and the cursor was then moveable acorss all the text:Welcome Message, Username, password etc but would not delete overtype or allow me to change the text in anyway again I was following the instructions from another post.
Is there a special key to be pressed to be able to type when attempting to edit a file or why would it not allow me to type?

The IP address I have been given to use for root access from within the office where the box is located I think is my own static IP address however the IP address to get root access from outside the office is completely different. How or why is this the case?

While I'm at it..... here goes one more question. Is there a comand that will will show the login history of anyone who has worked on the server that will enable me to identify who has been in it for how long and when. If so will it also identify the same info for person(s) logged into vicidial or vitiger?
Sorry if these are very basic questions and sorry that the post has turned into a list of questions and thanks in advance to anyone who is civil enough to answer.

[Op3r]

Just change the password of the server using the command passwd.

Now

In order for you to know who was the last to login to your server.

type

last



also you can change the username and password on your server to what ever you specified.