A Dropbox spokesperson said Tuesday morning, that the usernames and passwords were stolen from other services. The majority of passwords, according to Dropbox, had expired a long time ago. It is unclear at this hour how many usernames and passwords actually opened up a Dropbox account.
Even so, to better protect yourself, your best bet is to turn on two-step verification for Dropbox and other similar file storage systems. The two-step verification combines a password with a six-digit security code that is sent through your phone every time you enter your password. Additionally, Dropbox suggests that you use strong unique passwords when the need to create one rises.
Last week, a third party Snapchat webclient was believed to be responsible for the leak of 100,000 pictures that were said to contain teenage pornography. And two times in recent months, a large number of personal pictures taken by celebrities were hacked, even though the celebrities thought many of the pictures had been deleted. In those two cases, Apple's iCloud was blamed.
source: Dropbox via TNW via Engadget