For most ExtremeTech readers this should almost go without saying, but if you find a mysterious USB drive in your mailbox, don’t plug it in. There are more dangerous things a criminal element could drop in your mailbox, but a malware infected USB drive isn’t good. Police in Australia are investigating a series of thumb drives that showed up in mailboxes carrying some nasty ransomware.
Do not plug in USB drives if you don’t know where they came from. There are a lot of things that can go poorly for you.