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Is it widely known that in the opposite way (an unknown USB to safe pc) it could be really dangerous. But I can't find any info if is it dangerous to put a drive to other pc.

Case:

  1. I have my USB drive with some unimportant data to print.
  2. I put it into pc in copy point.
  3. I print my stuff.
  4. I take USB home and I format the disk.

By dangerous I mean: could my drive be infected in a way that cannot be repaired by format or even with more complicated "healing" process. In my case, I don't care about the data which is stored on that drive.

  • What steps do you take to ensure you can do #4 without the disk first infecting the PC you're using to format it? – dwizum Jun 18 at 18:39
  • My point exactly. Is it something I can do to prevent that? I can erase drive before unplugging it from pc in copy point but I guess it could be infected afterward nevertheless. – Jakub Mosakowski Jun 18 at 18:43
  • You are describing exactly the process of how to infect your home machine from some other infected machine. Many/most PCs are set up such that they will automatically read data from USB drives which are plugged in, which may/will result in your PC becoming infected. While it's possible to scrub the USB drive, doing so in a way that does not result in the possibility of becoming infected is non-trivial for most users. – Makyen Jun 18 at 19:43
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You said,

I can't find any info if is it dangerous to put a drive to other pc

Before anyone tries to answer that, we need to know what you consider "dangerous" to mean.

If you're concerned about the contents of the files you've put on the drive (including any metadata that may be attached to them), you need to abandon this entire idea, because there's precious little you could do to ensure the safety of that data. The files should be considered compromised as soon as you plug the USB drive into the unknown PC. Software on that PC could easily copy, store, modify, or send your files anywhere.

If you're concerned about making the USB drive safe to use in the future, you need to at least be cautious. Taking that drive home and sticking it into an average personal computer would be dangerous, as the drive could have been infected by malware that could spread to your PC before you had a chance to format it. This malware could then potentially cause problems by corrupting or stealing personal information on your PC via a variety of methods.

Information Security professionals and enthusiasts commonly get around this risk by "nuking it from orbit" - either literally destroying the USB drive after using it, or accessing it from a system designed for dealing with infected media and then securely erasing it. Many times, these purpose-built systems are just a boot disk with a lightweight OS that's pre-loaded with security tools - but, crucially, has none of your personal information, and no access to your personal information.

  • You are right, I added an explanation in the original post of what do I mean by "dangerous", in this theoretical case. – Jakub Mosakowski Jun 19 at 9:00
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Well if the USB drive is infected from the PC (which shouldn't be too hard, to write a program that does it in the background) then in step 4 your computer would be infected. Since you need to connect the USB drive to your or some computer before formatting it.

  • Um, the "does it in the background" part is easy, but the "USB drive is infected from the PC" part is definitely not easy. Not all devices with USB ports are interchangeable! The malicious sorts of USB devices are, aside from the form factor, as different from a flashdrive as they are from a printer or a joystick. The worst you could do to a flashdrive is either destroy it (if the PC's USB port sent an electrical surge), or write malicious files to it and hope either the user opened them, or that the user's computer had a vulnerability that triggered when the malicious files were mounted. – CBHacking Jun 18 at 23:49
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Short answer is no it's not safe, or yes there is some danger to what ya suggest doing with that drive.

  1. Is an opportunity for a compromised device to may be transmute your USB drive into a "bad USB", however, it's far more likely to brick the USB because it's hit'nd miss as far as drives that are able to masquerade as a HID.

A possibility, though very remote last I looked into such things in other-words.

  1. Your unimportant data is now likely within the logs of that printer, for anyone (with the know-how) to later access, and perhaps find a way to make it important to someone at a later time.

  2. If your USB drive was turned into a "bad USB" then this is where your home PC get's popped. And formatting does not generally wipe the stored data but instead removes the addresses to the stored data, with the proper tools such data could be recovered so long as it has not been overwritten.

If you're really worried about safety of USB drives being inserted into un-trusted devices I'd suggest looking into tools such as USB Guard for the PCs that you do own so that USB drives are not easily used as a HID attack method.

  • I've never heard of any example, even theoretical, of a USB host being able to "transmute" a typical USB Mass Storage device (such as a flashdrive) into any other class of USB device (such as a Human Interface Device like a keyboard, or a network device, or any of the other sort of malicious USB devices in the world). If you know of any such "transmutation" that works on a commercially-available flashdrive, do please share a link... – CBHacking Jun 18 at 23:52
  • Generally transmutation is done voluntarily and after much more research than a single guide on the subject can provide. However, considering that detection of compatible devices can be automated along with the other steps; it's not a question of if but when such thing'll be in the wild... really the best targets for such an attack are Android devices that get plugged into a charging station or similar then some days later toast the user to connect to their PC for syncing, hint CASUAL + NetHunter. – S0AndS0 Jun 19 at 0:05
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Well, if you plug-in your USB(Universal Serial Bus) stick into an unknown machine.. * it's now a part of the unknown machine.

You can take off it and drop on that machine, BUT. If an automatic process or a user detect that the usbstick is mounted while your device is not protected from machine-to-host data writing, it can happen that a your device get infected, with visible or hidden stuff.

if you don't want this happen, you can use a storage device that doesn't allow writing to, unless you know the password.

  • 1
    Your information here is inaccurate. Based on the information on the page you have linked, SanDisk SecureAccess is an encrypted storage within the filesystem already exiting on the USB drive. As such, it would in not protect you from having the USB stick infected by software on some machine. This contents inside the secure store might be protected, if you didn't enter the password into the infected machine, but that doesn't mean the data on the USB stick which is outside of the encrypted portion wouldn't be infected. – Makyen Jun 18 at 19:39
  • Maybe i was not clear, you have to use a stick that will block the second person from writing to that stick. – user211258 Jun 18 at 19:50
  • The vast majority of implementations where a password is required to access data on a USB stick are normal USB drives where the encryption is a software component running on the host computer and the encrypted contents are stored as a file within the normal filesystem on the drive (i.e. the USB drive is actually just a bunch of storage, like any typical drive/FLASH drive). The USB hardware would have needed to be designed to prevent access without having a password provided to the USB drive. This is significantly more complex then most drives and would be an explicit feature when purchasing. – Makyen Jun 18 at 20:17

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