Mostly from test sites, with added notes by me :
How To Protect Your Computer From Attacks
To safeguard your computer on the Internet, it is not enough just to install protective software and improve your system configuration settings. To be secure you have to learn and practice the following fundamental safety procedures:
1. Learn the security policies of your ISP (Internet Service Provider) and/or other respected sources.
2. Encrypt your e-mail, unless you're sending postcard material. There are many standards of mail encryption, but two of the most popular are S/MIME (Secure Multipurpose Internet Mail Extension) and PGP (Pretty Good Privacy). I would include EnsuredMail, for its ease of use and anyway, it's freeware.
3. Do not open attachments to e-mails from anonymous or unknown sources - unless you've saved them first and run your VScanner over them. Don't forget the usefulness of Popcorn and MoOutlook Security.
4. Do not download suspicious files from the Internet and do not execute them on your computer. Anything with *.exe, *.com *.bat (and others) regard with extreme prejudice and do not click, until you have taken the proper precautions (which could well involve Kevlar)
5. Only allow people you know and trust to use your computer (and how!)
6. Configure your Web browser for safe Internet operation. Have your browser ask or prompt you for confirmation each time it is offered a Java or ActiveX applet. Okay these only when you are visiting trusted sites.
7. Purchase, or download, software to protect your computer, such as an anti-virus scanner, anti-Trojan software and a decent firewall. For free versions of all of these, you know where to look....