Terminal: keyboard freeze when introduce password

The terminal has not frozen. The password entry does not show any feedback as you are entering in your password.

Simply enter your password then hit return/enter once you are done. If you make a mistake, press delete as many times as you think you need.

This is to prevent you cut and pasting your password length all over the internet when discussing terminal sessions (for example, if you have *** as your password entry, it would be very easy to break into your system).

As an extereme example

sudo ifconfig eth0
password:***eth0 Link encap:Ethernet HWaddr 00:26:B9:79:83:B5
          inet addr: 1.2.3.4 Bcast: 1.2.3.255 Mask:255.255.252.0
          inet6 addr: a::a Scope:Site
          inet6 addr: a::a Scope:Global
          inet6 addr: a::a Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:925354 errors:0 dropped:0 overruns:0 frame:0
          TX packets:394131 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1234567 (123.5 Mb) TX bytes1234567 (123.4 Mb)
          Interrupt:17

I could simply check if 1.2.3.4. was running a remote login then brute force out the 36^3 =46656 passwords. Chances are that the password is 123.