LinkedIn users can now add two-step verification to their accounts. The feature is designed to add another layer to the sign-in process when logging in from a new or unknown device. The changes come one week after Twitter introduced two-factor authentication following a series of recent hacks. Apple, Facebook and Google are among other Internet companies that offer two-first-factor logins as an option for users. Security experts had long been calling for the company to make it an option, but some security experts say it is not a panacea.”]