In heavily regulated organizations, new tool adoption isn t something you could historically accomplish without a rigorous procurement and testing process. We often see individual teams downloading and using collaboration tools that suit their needs with little oversight from governance and IT teams. Just by using Slack, a user could have widened the attack landscape for the organization without even realizing it. Companies should detect and block these cloud applications until they ve had time to assess them, after which they can be released in a controlled manner.
Source: https://threatpost.com/tackling-collaboration-conundrum/146603/