Sorry if this is the wrong forum to post this in. This is my first time posting on these forums and I don't know how much information you will need to resolve this problem.
I was wondering if there's a way to confirm if a USB flash drive is free of viruses, malware, and/or ransomware?
I used this USB flash drive back on Feb. 23rd with a computer (Windows XP) that was a part of a network. The server was infected with Ransomware and all the files on the shared network were encrypted on Feb. 25th. Supposedly nobody used any of the computers on the network on the 25th, so I suspect that the infection happened earlier and activated the Ransomware at a later date (I don't know if this is even possible).
I always remove the flash drive from the computer when I'm not using it, however, since I don't know when exactly the infection occurred, I really don't know if it was infected or not.
The tech that was hired was unable to decrypt the files and couldn't contact the hacker to pay the ransom, so we ended up replacing the computer with Windows 10 and restoring some of the files from an older backup.
There are files I'd like to transfer from the flash drive to the new Windows 10 computer (Computer #1) and to an older spare computer running Windows XP (Computer #2), as the backup the tech used did not have copies of these files.
After avoiding the flash drive for weeks, I decided to test it out on Computer #1 (Apr. 3rd), since I thought Windows 10would be more secure. After plugging it in, there was a notification saying "There is a problem with this drive. Scan the drive now and fix it." I ran Windows Defender and the scan detected "no threats" on the USB flash drive. I also ran a full system scan and it was also clean.
Since then, I have been saving documents to the flash drive and opening files on it (always while using Computer #1), but I've refrained from copying the flash drive's files to Computers #1 and #2 because of a lingering fear of infection. Every time I plug it in, I always get the same notification to scan & fix it, but every time I scan it with Windows Defender, no threats are ever found.
It's been over two weeks now since I've tried inserting the flash drive and nothing bad has happened to Computer #1 (or the rest of the network for that matter). I've avoided using the flash drive on Computer #2, because I worry Windows XP will be more vulnerable or the infection will only effect XP but not 10.
1) MAIN QUESTION: Is the USB Flash Drive safe to use (free of Ransomware, Malware, Viruses, etc.)?
2) Does Ransomware usually wait a period of time before activating or take awhile to encrypt files?
3) Are Windows Defender and Avast Antivirus even capable of detecting Ransomware or am I wasting time running scans with them?
4) Have I made a big mistake by opening files on the flash drive with Computer #1, and spread malware on the network?
5) Does Ransomware even make copies of itself and spread like viruses do?
6) I noticed is that the Flash Drive is supposed to have a size of 16 GB, but according to Windows Explorer, its total size is only 14.9 GB. Is this just false advertisement of the product, or is something wrong with the flash drive?
USB Flash Drive: SanDisk Cruzer Glide 16GB
Computer #1: Windows 10
Computer #2: Windows XP (Service Pack 3)
Windows Defender: Updates automatically (up to date) - for Computer #1
Avast Antivirus: Updates automatically (up to date) - for Computer #2
* The USB Flash Drive is usually plugged into a computer for 2 hours or less. I very rarely leave it in for a long duration.
Thanks for your help,