Dropbox is asking users who signed up before mid-2012 to change their passwords if they havent done so since then. The cloud storage service said it was taking the measure because its security teams learned about an old set of Dropbox user credentials. The move comes in the wake of several breaches including that of LinkedIn in 2012, which has led to concerns that email addresses and passwords used by people across accounts could be used to compromise other services. Dropbox is also recommending that users use two-factor authentication when resetting their passwords.”]