Can't open different Websites

Question

Hello,
if i try to open "www.facebook.com" or "www.ebay.de" it is not possible to open the website.
Every Website works fine! I have the same Problem in other Browsers. In addition it is possible to connect to facebook with an other notebook.
So i opened my Network-Diagnostic-Tool and try to Trace:
traceroute to www.facebook.com (127.255.255.255), 64 hops max, 72 byte packets
1  * * *
2  * * *
My MacBook try to open the IP-Adress "127.255.255.255" (the same happens with ebay)
This is my Routing Table:
Destination        Gateway            Flags        Refs      Use   Netif Expire
default            fritz.box          UGSc           18       10     en1
127                localhost          UCS             0     3126     lo0
localhost          localhost          UH              6    32906     lo0
169.254            link#5             UCS             0        0     en1
192.168.178        link#5             UCS             5        0     en1
What can I do to route Facebook, ebay to the correct IP-Adress?
I hope you could help me... thx!

Answer 1

You, or someone using your computer, hacked the system to block certain servers. The file modified is /etc/hosts. 
By far the easiest way to fix the hosts file is to restore it from a Time Machine (or other) backup that predates the modification. If that's not possible, then do as below. Please read this whole message before doing anything. 
Back up all data.
If you have more than one user account, you must be logged in as an administrator to carry out these instructions.
Triple-click anywhere in the line below to select it:
open /etc/hosts
Copy the selected text to the Clipboard (command-C).
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste (command-V) into the Terminal window. A TextEdit window should open. At the top of the window, you should see something like this:
# Host Database
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
127.0.0.1                              localhost
255.255.255.255          broadcasthost
::1                                        localhost
fe80::1%lo0                    localhost
Below that, you'll see some other lines. There should be nothing before the first line above. Make sure you scroll all the way to the bottom of the document. In OS X 10.7 or later, scroll bars are hidden by default until you actually start scrolling, so you may not realize that you’re not seeing the whole document.
If the contents of the TextEdit window are as described, close it, then enter the following command in the Terminal window in the same way as before:
sed '/lo0/q' !$ > Desktop/hosts
You should now have a file named "hosts" on your Desktop. Double-click the file to open it in TextEdit, and verify that it has only the contents shown above, with any extra lines removed. If so, close the window without making any changes.
Next, go back to the Terminal window and enter one final command, again without typing:
sudo sh -c 'cat Desktop/hosts > /etc/hosts'
This time, you'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. Confirm. Quit Terminal. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator.
That will fix the hosts file. You can now delete the file that was created on your Desktop.