When you've got a hot new online platform, you inevitably become a target for hackers. That's the lesson Slack, a popular business collaboration tool, learned when it discovered an intrusion in its systems last February. As a result, the company is now rolling out two-factor authentication, which adds another layer of security by making users enter verification codes whenever they sign onto its apps. Slack claims the hackers got into its central database, which contains usernames, email address, and encrypted passwords. At this point, though, it doesn't look like they were able to decrypt passwords. On top of making logins more secure, Slack is now giving leaders of its groups the ability to reset all of their passwords, or log their entire team out of Slack.