First check off these three statements.

1 - Is your firewall turned on?

2 - Do you have an antivirus program installed and running?

3 - And do you have antispyware and adwareprograms installed?

These are your general guidelines of making sure that your internet connection is secure.

Follow up:

The rest seems to be based on your activity on the web. The sites you visit and the things you do on the Internet largely determine whether you get viruses, adware, or spyware. If you do not do and P2P file sharing or visit questionable websites then you are about 99% secure because that is where most viruses come from.

Some people agree that Firefox is more secure that Internet Explorer. This is true about a year ago but now the marketing is moving over to Mozilla Firefox. The majority of viruses are made by companies and corporations trying to monitor what you do and to get you to buy their product by displaying lots of ads called adware. If you think that you do have adware, spyware, or viruses then refer over to my post: How to get rid of adware, spyware, and viruses the right way.

The chances of a computer getting a virus are very low if you know how to surf the web the right way. One of the biggest mistakes is that people run .exe files that they don't know what they are. When you download and run programs that you do not know what they contain, the potential of it having a virus is big. Never download questionable programs. If you want to get the program, first check out www.softpedia.com. This website puts only spyware free software on their website. The website is like a wikipedia for software. There are other file types that can install viruses on your computer but the .exe file are the most dangerous. This is why people say not to open attachments in emails.

Emails such as Gmail, Hotmail, Yahoo, and MSN do not allow .exe files to be uploaded, sent, or recieved. But they can be sent inside of another file such as a .rar file or .zip file. This is why people should avoid downloading email attachments. If you want to be able to view the extentions of file to see what they are refer to this article: How to Show File Type Extension and Why

For a virus to install on your computer, 99.9% of the time, it requires a click. Viruses use computer programs to install and run. If you do not install programs that you get from unsure sources then the chances of the computer getting a virus is slim. Download only from websites that are popular and clean.

Immunize your computer/web browser

There are some great free programs out there that can "immunize" your computer. One is called SpyBot Search & Destroy. Once you download it and install it, update the program. When you update the program it will give send the program all the known web addresses on the internet that link to malware. Once the program is done updating, immunize the computer with SpyBot. There are several ways that this program will block links to malware. One is that it will give Internet Explorer links to block and it will put blocked links the computer's Host file. The host file is in the system32 folder drivers >> ect. The Host file can be edited and added to. If you want to block certain websites, this file can be edited to do just that.

Conclusion

Remember that their may be other users that are using your computer. However, if you are the only user and you browse the web only on trusted websites you are bound to stay secure. Make sure that you download programs only from places like www.softpedia.com and www.download.com. By following these steps you should stay virus free and your Internet connection will be secure.