Answer by yanokwa for Feedback when typing password at a sudo prompt

On some UNIX-based systems, sudo can show an asterisk (*) when you type a letter.

In the terminal, enter...

sudo visudo;

Type your root password in (you won't see any visual feedback yet) and hit Enter.

Now, find the line that reads:

Defaults env_reset

And replace it with:

Defaults env_reset,pwfeedback

Finally save and exit the file. Assuming you are using vi, that command is:

:wq!

and then press Enter.

sudo should now be set up correctly. To test, open up a new terminal and type this to reset the sudo timeout.

sudo -k;

Now try it out.

sudo ls;

Source: http://whyareyoureadingthisurl.wordpress.com/2010/05/16/sudo-and-password-feedback/