Hacklog Volume 1 Anonymity: it security & Ethical Hacking Handbook

2.2 Hostname
Usually, a hostname is configured during the installation process. However,
in  some  cases  such  possibility  is  hidden  from  Windows,  MacOS  and  Linux
Operating Systems.
The hostname is an identification name we can specify for a device, to see its
role within a network: however, this piece information is often left to chance, so
we can usually find the username (on Mac, we will read something like Stefano-
MacBook-Pro.local), the Operating System in use or other data we may want to
keep safe from other people in the LAN.
2.2.1 Changing the Hostname
In  any  Linux  and  MacOS  distro,  the  command  we  can  use  to  know  our
hostname is... hostname!
$ hostname
The latest release of Debian has integrated the systemd command, then you
can also use:
$ hostnamectl
and  you  will  learn  more  about  your  Operating  System,  including  static
hostnames, machine IDs, the GNU/Linux version in use, your architecture, etc.
The  hostname  command  also  allows  you  to  temporarily  change  the  value  by
typing:
$ su
$ hostname [newhostname]
You can verify such change running the aforementioned commands again, or
closing and reopening the terminal session. If you need to permanently  change
the computer hostname, on Linux you can use the command:
$ su
$ sysctl kernel.hostname=[newhostname]

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while on macOS it will be:
$ sudo scutil --set HostName “[newhostname]”
As we will often see throughout the course, Windows manages information
in its own way. In this case, you have to right-click the Computer icon and select
Properties.  You’ll  find  all  the  hostname  information  in  the  screen  under
“Computer Name, Domain and Workgroup Settings”.
2.3 Domain Name System
Before  the  invention  of  DNS,  if  you  had  to  access  to  a  computer  in  a
network, you had to know its IP address, namely a set of numbers identifying an
IT device in a network (we’ll cover it shortly). As devices increased in number,
it  became  impossible  to  remember  such  sets,  therefore,  in  1983,  a  new  system
was  created  in  order  to  help  memorizing  them,  using  a  unique  name  (i.e.
inforge.net) instead of the reference IP address (such as 192.124.249.10).
It was the birth of DNS logic and the related DNS servers, which translate a
domain  name  into  the  matching  IP  address.  Domain  is  not  referring  to  the
website only, but to the entire network – we use the term domain to represent an
entire  network  consisting  in  computers  that  share  the  same  logic  and  the  same
rules  enforced  by  their  admins.  For  now,  you  only  need  to  know  that  your
computer or Internet network will only respond to the DNS given by your ISP,
unless it is explicitly expressed.
As we are going to see, one of the major threats to users privacy online are
Internet  Service  Providers  (ISPs),  for  this  reason  you  should  replace  the  DNS
you  are  using,  whether  you  want  to  be  100%  anonymous  or  not.  Furthermore,
you  should  consider  the  huge  advantage  in  terms  of  response  offered  by  more
efficient  and  trusted  alternate  services.  As  you  may  have  noticed  for  many
websites,  in  order  to  accelerate  governmental  takedown  operations,  the
competent bodies commit to directly censoring a domain resolution from a DNS,
rather than blocking the related serves: it already happened for many sites (like
The  Pirate  Bay)  and  it  will  keep  on  happening  in  the  future.  Using  unfiltered
DNS, you’ll be a little more anonymous and automatically access to a complete,
unfiltered list of all the websites actually available on Internet.

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2.3.1 Choosing DNS
You can use two types of DNS: public and private ones.
Using public DNS you will improve your anonymity and privacy, and your
DNS requests will be faster, with a safer navigation (if you are concerned about
malware-filled sites). Public DNS usually leverage two IP addresses, known as