service

It could be that one day we may be required to access a service or website in a quick or easy to remember, or simply for the reason it does not work via the Internet or our local network, or perhaps we need the opposite. Will give us some examples where this technique can be useful;

• As access control, to block certain web pages, navigation restrictions in a company (hotmail, facebook ...), parental control (sex, inappropriate content ...).
• Access to websites using a name (URL) shorter or easier to remember.
• To block some websites advertising. Related to the first option, but with a different purpose.

We may also find that a malicious application modifies the hosts file without our knowledge to disturb and modify the behavior of our team. Like virus (worm) MyDoom , which modify the hosts file to prevent access to websites that we could about security or antivirus (among other things).

This file can be found in almost all current systems;

  * Windows 95/98/Me: C: \ Windows \ hosts
     * Windows NT/2000: C: \ WINNT \ System32 \ drivers \ etc \ hosts
     XP/2003/Vista/7 * Windows: C: \ WINDOWS \ system32 \ drivers \ etc \ hosts
     * Windows 64 XP: C: \ WINDOWS \ SysWOW64 \ Drivers \ etc \ hosts
     * Unix / Linux / MacOS (in general): / etc / hosts 

I can change it with any text editor. Where, for each new line to add next and enter an IP (separated by a space at least) the name and URL you want to use.

By default, the hosts file has some comments that start with the # symbol in front line and has at least one entry (line);

  # Comment in the file
 127.0.0.1 localhost 

Suppose we want to access a resource that we have a PC / server to a local network, but do not want to use the IP and know his name or can not access it for whatever reason (problems with DNS servers ...). To fix it must suffice to add an entry with the server IP and next to the name you want to use, can add as many lines as necessary, but each can contain only one IP. For example;

  # Comment in the file
 127.0.0.1 localhost
 Server 192.168.0.1 

From this moment we can access the PC acting as a server named "server". On the server IP is 192.168.0.1 and the name you want to use to access the resource would be "server".

To block all content from a website or access a particular service as might be the chat messenger, hotmail web page, facebook, twitter and prevent computer users from accessing services that want. We could do with these entries;

 # Block these IP addresses pointing to an invalid 0.0.0.0 facebook.com 0.0.0.0 hotmail.com 0.0.0.0 ads.publicitat.com 

Apart from the hosts file, find a file in the same folder called networks, which has a function similar to the above, except that in this type a name and redirects to an IP address.