First off let me just say that I've worked at some of these companies. I'm here to explain to you how to secure your Windows machine.
First things first, STOP USING INTERNET EXPLORER AND EDGE!! They are the gateway to every malware infection known to man on a Windows machine. It does not matter if you're using the latest and great from Microsoft, Microsoft is not in the business of creating secure software, they create an industry that creates jobs for thousands upon millions of people. If you need a browser stick to Chrome or Opera.
Do not use Firefox it is also insecure. The two things you will need on your browser is a adblocker, preferably uBlock it uses less memory in the browser that Adblockplus. Also add Stop-it.be to your browser, the Stop-it plugin will stop any malicious pages from even loading because it does a comparison of the domain name to a block list if the site is on the blocklist then it will not load, (ie. those fake error message popups you get when you're browsing the web).
Secondly, get rid of your McAfee and Norton subscriptions, both of those companies create software that is complete bloatware and it creates more problems than solutions. If you want an anti-virus that is reputable stick with F-Secure, Bitdefender or Kaspersky. Webroot is also ok as well. I would also recommend installing and purchasing Malwarebytes and have that running on the machine as well.
My next suggestion would be to prevent ransomware purchase AppGuard it received 2 awards from Homeland Security for malware prevention and infection (http://www.appguardus.com). My next advise would be to be extremely careful when installing software you download off the internet, most of the software you download also installs toolbars and other malicious software (trojans, adware..ect..) onto your machine while it is installing the legitimate software you intended to install. PAY CLOSE ATTENTION TO WHAT THE SETUP IS ASKING FROM YOU DON'T JUST CLICK ON NEXT!!. Periodically close all your applications on the machine once or twice a week and run Ccleaner both the cleaner portion and the registry portion as well.
I would also run ADWcleaner on the machine every other week, this will get rid of any adware or toolbars that may have gotten installed (Adware Removal Tool is good too). Backups, buy yourself a backup drive and take the time to create a reliable backup, drives now are extremely cheap you should have no excuse to not have a backup. If you do any banking online, I would suggest looking into installing a program called VirtualBox which allows you to install a secondary operating system (Linux -preferably Ubuntu) if you have the time look up Tails, you can also go to Youtube.com and search for how to set a virtual machine up using Tails. Once you've done that you can then load up a browser using that virtual machine (operating system) and then do your banking.
This creates a gap between your host operating system in this case Windows and your banking operating systems in this case the Linux VM. This prevents any leaks in data along with any type of malware or trojans from pilfering your banking information. On another note, consider learning and taking the time to use encryption whenever possibly, if you are browsing the web and you notice that a website does not have a little lock next to where the website domain name is on the browser then you know that the site does not have a certificate and has not been verified by a third party to being secure, in this case they are not using encryption meaning that your data will be sent over clear text -WHICH IS BAD!! (Please visit the EFF.org to learn more).
If you are smart you will join Bleepingcomputer.com's newsletter which will keep you informed of the latest changes that arise with in the malware detection community along with providing you with an endless amount of information regards technical details on how to handle certain circumstances on your machine. Next up, the Windows firewall, make sure it is always enabled. A side note for updates, Windows Updates if you're on Windows 7 should be set to automatic. If you're worried about the forced Windows 10 upgrades then I would suggest using GWX Control Panel so that you can disable that easily (http://ultimateoutsider.com/downloads/).
For you Mac users it's real simple. STOP USING SAFARI FOR YOUR BROWSING!! Again download Chrome or Opera and use those browsers instead and again install uBlock and the Stop-it.be plugin. If you have to use Firefox, but for gods sake don't use Safari.
Apple has taken a backseat to Safari in regards to code changes . Hence the reason they've come out with a technology preview of Safari, meaning that they have start to overhaul most of the code for it. Both Chrome and Opera use the same backend rendering engine which is Webkit, which is open source, same goes for Safari, unfortunately Apple is taking there time with Safari code changes. Second, enable the firewall on your Mac.
Third, if you run Bootcamp or are sending files to and from Windows to your Mac machine consider installing an anti-virus (ie. Sophos or Webroot should be fine). Third, if you use a Mac especially a Macbook ENABLED THE PASSWORD ON YOUR MACHINE!!! Not having a password on your machine is extremely insecure.
It's like not having a pin number for your debit card, its just plain ***. When creating your password consider using a password manager, I currently use 1Password there is also Msecure which is also a great one too. Install those and use them, incorporate them into your daily routine when using your Mac. Consider also using a password policy (which can also be use on you Windows users) my password policy is set for every 40 days, meaning that every 40 days I generate a new 16 character password, and save it into my password manager.
I've known people that are paranoid and use pen and paper, which to me is insecure depending on how you handle that medium, the person that I knew that did that, used a blackbook and then put that book into a safety deposit box in his home. (just something to consider). Again, encryption goes hand in hand with being secure online (Mac user scroll up to read the previous explanation). Backups, the Mac operating system has a great feature called Time Machine learn to use it, it will save you aggravation if your system crashes (haha).
Your iCloud password, again use that password manager so that you d not forget it. As for removing malware from your Mac, simply download and install Malwarebytes for Mac and scan the machine if it finds something it will remove it. Again if you stop using Safari you should not fall into this category. Mackeeper is TRASH!!
Do not install Mackeeper it is fake, unreliable, software that does more harm than good. Consider spending some money on two pieces of software Little Snitch and Cocktail. Little Snitch is an application based/rule set firewall program, it does have a learning curve but again use the free resource like Youtube.com to learn to use it, you will be able to control what programs have access to the intranet/internet. Cocktail is a great piece of software that does all the maintenance for you, you set it up and let the scheduler do the maintenance on your machine.
And last but not least, if you have a desktop Mac SHUT THE MACHINE DOWN COMPLETELY!!. If you have a Macbook you can use the sleep function but again I would shut it down, shutting the machine down clears out the cached data out and allows the operating system to start with a clean slate (if you install cocktail make sure to let that run first then shutdown). Well, there is a lot more I could go into in regards to your Mac, but this should be enough for the common user.