Can someone access my personal files or see me chatting from another computer if they use our internet access--My computer says a wireless computer is trying to access the internet through my hookup?

Answer 1

If someone has access to the data stream from your computer to any servers you connect to, then yes (in the example of wireless connections). Although it's unlikely they can control your computer, it can see what information you are sending or receiving.

You can prevent someone accessing your computer by using a simple firewall, and to prevent someone accessing the data stream, you should use an encryption key. The instructions of how to do so should be on the software manufacturer's website. (microsoft = microsoft.com) Use SSL connections when available to ensure security. And never place personal information over a non-secure connection. The way to identify a secure connection is simple, most Web Browsers have a logo meaning security is enabled. It is usually a closed padlock. These icons will be found either on the address bar or on the status bar.