First, let me start off with the Notion that All Antivirus sucks. Regardless of the brand, or the Reputation, If you gave me an hour or less and a windows PC with any Antivirus app on the market on it, pay or free, I will give you an infected box. So why does this happen?
1) Hot, Fresh, Just for you! This is not just a slogan you see on McDonalds made to order burgers anymore. Today's Virus Obfuscation techniques are so fast and random, that when you activate an payload dropper (whether it be a Flash, Java, Website, Browser exploit or even a Trojan installer) The Payload that you get will only be statistically seen only once. You and only you will get that version of the virus even though it's using a well known virus kit that would be detected if it was not obfuscated. This technique is the reason why no AV firms detect the Fake antivirus variants or FBI Warnings or cryptolockers of the past even though all of the major codebases were detected by most AV Firms.
2) I'm an Necessary App! People need me to change their search engine, hijack their DNS, spy on them, and pop up ads randomly all over the screen and websites! Read the Slashdot Journal link for some insight on how adware gets on people's PC. Let me make something clear here. Adware is a Virus When a customer comes into my shop and has something like Conduit searchprotect, or Wajam on their machine, I tell them that's a virus because it is. They didn't want it, they got it and it's doing things they don't want. Sounds like a virus to me, yet just about every AV Firm ignores these and lets them gleefully install because they're afraid of getting sued by one of these companies so instead they make guidelines to let them slip through. The first AV I find that reliably removes all Adware as well as viruses without me having to manually remove them or fallback to a removal tool (like ADWCleaner, which is now starting to miss stuff as of late) I will sell in my store.
3) In Soviet Russia, Trojan Exploits You! This Journal link has been on my sig for years now, and is the primary reason why AV doesn't work anymore. This week alone I had no less then three of my customers Directly call Fake Support Scammers because their PC / Printer / Camera didn't work, and they called the phone number on the first link (The Ads) they saw when they searched for "(PC / Printer / Camera) Support" and if you're letting the bad guys in to physically touch your own box you're already screwed and no AV on earth is going to save you.
Right now, I'm telling people three things:
1) Install MSE All AV sucks, The only question is how much do you want to pay for something that sucks. MSE is free, at least blocks most of the ultra bad stuff and doesn't pop up ads of any kind so it's what I install.
2) Install Adblock on all browsers I install Adblock Plus on any machine that leaves the store. if you're going to infect yourself chances are an Ad is going to lead you there. Blocking the ads blocks most of the infection vectors off the bat.
3) Don't Download or Install anything. There is no safe place I can direct people to download files without getting some sort of Adware Virus. This is easier to tell users rather than pay attention to what you download. (See #3 to understand) If they protest, go to your PC, go to ask.com with your adware blocker turned off, type in any program you would think they would download (I use VLC Media player. It never fails to show me adware links) and have them pick the download link, when they get it wrong (chances are they will) download the file and send it to virustotal.com. chances are one of the scanners will detect the Adware dropper from the fake site, Then drill it home about not downloading anything.
4) Another alternative OS isn't going to save you This ancient Journal entry Explains why. Coupled with the other two Journal entries it should paint a pretty good picture that at this point in time, the user itself is the greatest threat, and if you read #3 you know you cant (legally) patch stupid. While an alternative OS (like Linux, OSX or even Chrome OS) can minimize exposure, it does not eliminate it and it will get worse as the OS gets more popular. You also still have a user in control and the Computer user laws apply. I've seen viruses for all three above listed OS'es (yes even Chrome OS. There are some nasty Chrome extensions out there and they infect all of you're logged in chrome Browsers)