host file cleared itself? how?

I've blocked some really annoying sites such as ad.doubleclick and other stuff ever since the beginning of time on my host file, and i've recently used it to block runescape so that my brother can't play it. Today while surfing the web I noticed that ad.doubleclick was unblocked. So i went to the host file and find out that everything I've blocked was gone. I quickly blocked everything again, (my brother hasn't noticed that runescape is unblocked) I lied to him that the "virus" (which I wrote) had prevented him from going to runescape when I finally destroyed it a couple weeks ago.

So, only my brother and I uses this computer, and I know for sure my brother wouldn't touch the host file. He had once wanted to clear space to download a game and deleted stuff from the WINDOWS file, and made the computer crash whenever you try to open it. In the end I had to reformat it. and I warned him to not touch anything in the WINDOWS file.

So, this comes to the conclusion that host file cleared itself somehow, i don't think my computer is infected with virus, because norton did not detect anything.

So how can the host file clear itself?

...Dude, Norton...?

Get something better....please....

...Dude, Norton...?

Get something better....please....

Yeah nothing is better then Norton.

As for those adds, if you are using firefox you may just want to get addblockplus.

Yeah nothing is better then Norton.

As for those adds, if you are using firefox you may just want to get addblockplus.

Avast is waaay better.

[COLOR="RoyalBlue"]S'cuse me?

There's loooots of things better then Norton.

Norton takes up a lot of RAM too, so it lags most computers.

For a few: BitDefender, AVG, Kaspersky, Avast, etc.[/COLOR]

um this thread isn't about wether norton is good or not, it's about how host file cleared itself, which still haven't been answered...

Yes it is. Your Norton might not have spotted the virus.

what kind of virus only clears the host file and does not do anything else?

How do you know it only did that?
Maybe it cleared the host file to get access to a certain part of your computer. Or something.

Get Avast, srsly.

It could've been something simple like disabling a form of host protection in another program. A good way to re-block most of the dangerous sites through your host file is to use Spybot Search and Destroy's 'immunize' feature, or for added protection to use the immunize in conjuction with a program called Spyware Blaster.

If you already have those programs maybe somehow you or someone else disabled the host file protection.

Check your C:\windows\system32\drivers\etc folder and see if there is a hosts.bak

Myself, I don't use any antivirus sofware.
I just use AdBlock Plus on Firefox