If you're so concerned about the security of your Dropbox account that even two-factor authentication through your phone seems too risky, you can rest easy. The cloud storage outfit has added support for USB keys as part of the two-factor sign-in process. Rather than punch in a code, you just plug in a stick to prove that it's really you. You'll need a key that meets FIDO's Universal 2nd Factor standard, but this key will also work with Google and any other U2F-capable service. Frankly, this is a long-due upgrade -- if you regularly access Dropbox from PCs, you won't have to worry quite so much that someone will get your login details and swipe your files.