The safest option is obvious, don’t try to access its contents, but if you absolutely had to, what steps would you take to minimize/contain any potential harm to your device/network?
AFAIK computers with normal setups won’t auto-run anything on a flash drive you insert. At most they’ll prompt you to ask if you want to run something. (Say no.)
So, it’s pretty safe to look at what files exist on the flash drive. Then you just have all the various exploits that exist with unknown files. Obviously, don’t run any executables on the drive. Don’t double-click on anything that looks like it’s a document (say PDF or word doc) because it might not be. To be extra safe, even if it is actually a PDF or word document, don’t open in the standard program (word or acrobat) because there’s a slight chance it might be an actual PDF that exploits an unpatched vulnerability in that program.
If I work in Iran’s nuclear program, and found this flash drive on the ground outside, I’d be a lot more cautious and maybe do some of these extremely paranoid things people here are suggesting. But, if Aunt Jenny was just over for a visit and I found a flash drive in the hallway near her room and want to check to see if it might be hers, it’s probably safe just to insert the drive take a quick look and not click on anything.
The problem is - is it just a mass storage device? Or is it maybe also a USB keyboard that will try to enter some payload? Or maybe it even contains a radio, and can communicate with an attacker nearby?
You can’t tell from the outside which protocols a USB device implements.
You can fit all of that functionality into the space of a USB-A plug - so if it is a thumbdrive you have way more space to work with than you ever need.
At minimum restrict your computer to only loading mass storage drivers - but as you quite likely habe USB input devices it is just a lot easier to investigate such a device on something like a raspberry pi.
Or, maybe it’s a tiny thermonuclear device cleverly disguised as a flash drive. Or, it might be a living, breathing creature that has evolved to mimic the look and feel of a flash drive but will detach itself from the computer and attack you at night while you’re asleep.
If you’re working with the Men In Black, you might have to consider these things. For the average person, it’s almost certainly just a flash drive and you can take reasonable precautions and be more than reasonably safe.
No lie. Unless it’s in a dedicated corporate parking lot, just fucking plug it in. Everybody here acting like they’re gonna get Stuxnetted. Yeah guys, we know the possibilities.
