main ways virus infects?

what are the main ways a virus gets into your computer and infects it? thank you

A wild virus infects its target computer through many ways/sources. The most common is infection through removable hardware (flash disks/USB), CDs/DVDs and others because they're being plugged into different PCs. It's like having multiple partners, getting AIDS/HIV from them and infecting each other. To prevent infection, it is advisable to disable AutoPlay (AutoPlay - Turn On or Off) and install security software (antivirus, firewall).

Another way or method of getting viruses is infection is through the Internet, if your PC is without security software, and if you are without common sense then you are highly susceptible/vulnerable to zero day malware attacks, exploits, rogues, trojans etc. To prevent such attacks, install security software, always keep Windows Update turned on, and add a DNS service (Norton DNS, Comodo DNS) which can block malicious websites known to spread viruses.

Hope this helps

Java Script and Flash. That is why it's good to be able to selectively block both. That is why I think Firefox with noscript is a great way to protect yourself.

One mistake some people apparently make is using a browser other than Internet Explorer - and then not installing security updates for IE because "well I don't use IE at all."

Big mistake, since IE is so tightly integrated into Windows and many apps out there make use of the IE code (usually for simple HTML displays within their interface or for making connections). This isn't always readily apparent, either - so it's important to keep everything that's on your computer up-to-date whether or not you use it. You may not, but the system may.

By not understanding how a virus/etc can get on your system (ignorance sounds more rude but is much more appropriate)! So you appear to be much smarter by asking and hopefully reading about viruses, malware, and countermeasures, than most members who just want to know what the best anti-virus software is and which one is 100% effective.

Oh and you'll need to leave any tendency to blindly trust anything on the outside of the monitor! Learn to be aware.

Good Question! (and answers)
Mike

Volume 11 of the Microsoft SIR (Security Intelligence Report) includes the following information:

Java Exploits
Adobe Flash Exploits

Also related is my blog post, How Windows PCs Get Infected with Malware.