Someone started controlling my computer over the Internet

★ wanayoo — archive 1999 http://www.howstuffworks.com/question179.htm

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Question

I was surfing on the internet when suddenly somebody took control of my computer. He was opening program's, printing things and asking me questions. How is it possible that someone can do this, how can i stop him and how can i prevent it from happening again? Please help me out here.

Answer

There are two "Trojan horse" type programs making the rounds right now. They are called Back Orifice and Netbus and they could both cause the behavior you are describing. BO and Netbus are Windows 95/98 applications designed to allow other people to access your machine (generally for malicious purposes) over the Internet.

In order for anyone to use BO on your machine, you have to install the server side of the application. This is normally done by getting you to download an application or by sending the server EXE to you in an email message and hoping you execute it. This is why it is called a Trojan horse - you have to consciously or unconsciously run the EXE to install the server - it does not propagate itself like a virus (see How Computer Viruses Work for a description of Trojans and viruses). Once you execute the server EXE the server is installed and will start running automatically every time you turn on your computer.

With the server installed, an evil-doer can run the BO client program and control your computer remotely. The evil-doer can run programs, erase files, etc. Obviously this is not a good thing...

It is easy to detect BO either manually or with software. These links will help you learn more:

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