Last week a ransom virus got spread through several large Dutch websites including large media sites (sites from national newspapers and other news media). And the culprit, the source of the infection, was none other than an online advertisement.What is a ransom virus you may wonder? It's a small piece of code which encrypts as many files as it can get access to rendering those totally useless. The only given way out of this is to contact the hijacker, transfer them a lot of money (real money, no rupees) and then you can hope to get the unlock key in order to decrypt your stuff (there are more solutions, read on!).And the disturbing part is that it got spread through websites which many people would describe as trustworthy and credible. And that is exactly the key of the whole problem... You may trust the website and its owners, but that trust can't go as far as the advertisement section because you simply have no idea where its coming from. Worse yet: in many cases even the owner of the site itself doesn't know!AdblockersAn adblocker is an extension in your browser which targets specific sources of advertisement and blocks them. This usually results in less clutter on some sites (no distracting flashing stuff) and most of all: less risk of getting into contact with unwanted stuff.As hinted at above: use of an Adblocker has far surpassed the mere function of blocking annoying material. In my opinion it has already entered the regions of security software, right along side virus scanners and such. It's really not an issue if you trust a website or not, you may trust the website and its origins, but there is no way what so ever for you to know where the advertisements are coming from.And, as can be seen time and time again, the moment something does go wrong on that end then many websites suffer.The solution?Use adblockers. A well known adblocker is Adblock Plus but there many others out there as well. And if a website now shows a pop-up asking you to disable it, otherwise you won't be able to enter? Each to their own, but I usually remove those websites from my favorites and start looking around for other replacements. I value my security over the revenue of some stranger, thank you very much.What if you have been hit by the ransom virus?First and foremost: backups. If you value your data you keep a backup copy somewhere, its very important. Heck; just get yourself an external HD (those shouldn't be too expensive these days), set up a list of files which you want to secure and leave your PC on for a night allowing it to copy all your data while you're vast asleep.I know what some people are thinking: you got websites such as Dropbox, Onedrive and Google storage, but you don't want to use them for this. That is: it can be a good way to keep some of your data secure, but if you value security you'll rely on an offline backup first and foremost. Why? How are you going to retrieve your valuable data when your Internet connection is down, or when those storage sites are suddenly performing maintenance?Don't say that it won't happen. Trust me: Murphy's law is key here.No backup? Don't despair if you're a Windows user!Microsoft does a lot of things wrong, but there are plenty of techies working for them who do know how things (should) work and how to provide a decent feature. Sometimes it's not all bad what they do, and one of those features is the file history (I only know the Dutch name, sorry):Right click on a folder, pick its properties, then find this tab somewhere. Its probably called "Recent versions" or something.Wonder what this is all about? Windows (from 7 and up) knows a feature such as "restoration points", it allows the OS to create a snapshot of the current situation and in case something goes wrong you can revert the OS back to that specific point in time. It can be a good solution if you installed a program which ended up causing chaos and you want to make sure that you get rid of it completely.Another related feature are the recent files. Whenever a file changes then Windows keeps a snapshot (provided that there's enough free space) and will hang onto it as long as you don't request those to be removed or if free space runs out. Sometimes this allows you to retrieve a file even if you removed it months ago.And if you got hit by a ransom virus then this can definitely provide a solution. Use the described procedure to reach this area, open the folder at an earlier date and check what files you can retrieve.Bottom lineAdblockers are no longer merely meant to block annoying advertisements: they also help to keep your computer safe!