USB flash drives are, undoubtedly, amazing tools that improve our portability and allow us to easily transfer files from one computer to another. With an ever-growing popularity, they are used by everyone and are becoming a preferred target for hackers and other cyber criminals to plant viruses and other harmful code.
But how exactly do these infections work, anyway? They take advantage of a feature implemented by Windows developers over time: Autorun. Even though this feature is somewhat handy, since it runs the media we insert in our computer automatically, these infections are placed alongside the autorun instructions so that whenever the device is autorun, those instructions will also be run, infecting the whole machine. Given that flash drives are meant to be portable and used in a lot of different computers, it is quite easy to understand how big of a problem these infections can be.
The key action: Prevention
Ok, it might seem obvious and common place, but prevention is the key here. Like you should always do online, be careful with the sites you visit and the files you download and place on your USB sticks. Also, be sure to have a protection system enabled on your computer, with an updated antivirus and, if possible, an enabled firewall.
Whenever you are in doubt if a file is safe, do scan a file with your antivirus software. In addition, you should periodically scan the entire flash drive for infections as another important safety measure.
Protecting Your Computer
So now, after the preventing part is done, your USB stick is clean. But what about all the other sticks other people put in your computer? Some antivirus programs do scan a USB stick as soon as it is plugged in, but some others (especially the free ones) do not, so even if you scan the drive after plugging it in, by that time the autorun programming has already been run and your computer is infected, which means that this way is not good enough.
Luckily, someone has this covered: let’s meet USB Immunizer, developed by BitDefender Labs.
USB Immunizer is a small piece of software that just silently sits on your taskbar and acts when needed, that is, when you plug in a USB stick. The program’s action is simply to stop the triggering of autorun of USB flash drives. It also has an action to “immunize” them.
But what does this “immunization” consist of? Usually, the autorun information is stored inside a file named autorun.inf, which is hidden. This file can contain harmless information such as the drive’s name or icon, but it can also be used to place a harmful piece of coding in order to spread viruses, malware and other infections. USB Imunnizer’s immunization process securely replaces the autorun.inf file by a clean one (also hidden) which, due to some technical tricks, Windows cannot mess with – it cannot be deleted or overwritten, unless the drive is formatted or accessed outside Windows. As it turns out, there can only be a single autorun.inf inside a drive, which means that there really is no way that Windows creates another autorun.inf file. Inside the software, immunization happens as the .gif below shows:
After immunization, autorun.inf, which is usually just a file, is now turned into a folder, just like the screenshot below illustrates (in order to see it, you have to set your system to visualize hidden files):
USB Immunizer comes with an option that, when enabled, automatically immunizes all the new USB flash drives plugged into your computer so that you do not have to do it every time “by hand.” The program is available in several different languages, but it cannot be changed whatsoever, even in the menu: instead, it sets its language according to the operating system’s Region and Language settings.
This is a free program working on all Windows versions, so be sure to take a look and improve your computer’s and USB drives’ security.
Diogo (@diogocostaweb) is a Biologist with a grip on computers and technology. Running Windows systems all his life, has a big interest in discovering new apps that increase productivity or simply make things more interesting. He lives in Portugal and has photography and music as main hobbies. He is also the author of the page techkern.tk, a page for short (but useful) computer tweaks and tutorials.
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