It’s always important to remember that clicking on links, files and media that you are not absolutely sure of may result in serious damage to your devices.
Specifically, there is a new breed of malware called ransomware which may take control of your device and demand a payment to release it. Examples of this include CryptoLocker, which has been taking files hostage since September 2013.
https://www.us-cert.gov/ncas/alerts/TA13-309A (and yes you can click on this link!)
I would also ask you not to share USB drives if you are not sure that the drive is clean. All drives should be scanned by your anti-virus, but there are still zero day exploits that could be resident. It is much better to use the gdrive.
Also, please remember to advise your family and friends where you can of these kinds of things.
For more information on CryptoLocker, check out these links: