Addressing the Invisible Security Problem of Open File Shares

According to a recent survey from the Cloud Security Alliance, cloud issues and misconfigurations remain the leading causes of breaches and outages—and 58% of respondents report concerns about security in the cloud. Their worries are well-founded.

Nearly every day, we see examples of a company’s sensitive data spilling out of leaky clouds. According to my company’s July 2021 Cloud and Threat Report, “More than 35% of all workloads are exposed to the public internet within AWS, Azure and GCP, with RDP servers—a popular infiltration vector for attackers—exposed in 8.3% of workloads.”

The core to targeting cloud security failures at their root is an assessment of configuration errors. However, organizations should be doing more to hold up their end of the shared responsibility model for cloud security with file sharing. Broadly, clouds offer two kinds of file sharing. You’re likely already familiar with file-sharing in software-as-a-service (SaaS) applications. Equally important for the topic here are storage objects in infrastructure-as-a-service (IaaS) or platform-as-a-service (PaaS) clouds—they can be shared, too. I’ll explore IaaS/PaaS sharing in a later article; for now, let’s turn our attention toward SaaS.

Change your SaaS application’s sharing defaults

SaaS-based file-sharing services (e.g., Microsoft OneDrive/SharePoint, Google Drive, Box, Dropbox) have decided to make sharing as easy as possible. If Alice can access a file, then in almost every instance, she’s probably able to create a sharing link to that file and send it to Bob—or to anyone else in the world. Bob can click the link and receive some form of access to the file.

Why would SaaS vendors do this? Likely, it’s a business decision to minimize friction and maximize utility. SaaS vendors want to encourage as much engagement as possible on their platforms. They also want to limit the number of calls to their customer help desks. Logical business reasons explain these choices, but at the same time, the choices create security risks for the organizations that use these applications.

SaaS applications are bursting with sensitive information (sometimes literally). The challenge for businesses is to balance the demands for easy sharing with the requirements to keep sensitive information secure. The best way to achieve that is by changing the application’s default sharing configuration.

For example, in Office 365, you can disable sharing with users outside of your organization. When I was a Gartner analyst, I would encourage my clients to completely disable external sharing for OneDrive and to individually disable it for all SharePoint sites except those expressly intended to contain content exchanged with external participants. The reason for constraining external sharing to SharePoint is that it offers better control and tracking than OneDrive.

Of course, when you do this, you’re going to have to educate users who may already have some familiarity with the platform. Even if they use the same application at home and they’re accustomed to being able to freely share things, corporate instances of common SaaS applications need more control placed around sharing for the organization to rightfully protect sensitive information.

Another option to monitor and control file sharing

Organizations that add SaaS security posture management (SSPM) to their stable of security tools can continuously evaluate all new file shares to make sure the shares aren’t exposing sensitive information—even the shares that are permitted. It’s still good to double-check. It’s also good to routinely check which users have access to which sites and remove entitlements that are no longer needed because, for instance, someone’s job role changed.

If you’re disabling external sharing of all SharePoint sites by default then creating an exception in which an individual can place content in a site that permits external sharing, it’s important to continuously scan that to ensure sensitive information isn’t appearing in the permitted externally shared site. As “systems of sharing” grow ever more complex (such as Microsoft Teams), tracking the movement of sensitive information becomes difficult. SSPM can ensure that your policies are consistent across all your cloud applications.

Next time, I’ll investigate how a closed-by-default mechanism routinely lofts businesses into the headlines.

This article was originally published on Forbes Tech Council