Secure Document Sharing: How to Securely Share Sensitive Documents

  Secure Document Sharing platforms

When people think about secure document sharing, they usually think about specific secure online document sharing or collaboration services.  However, even confidential document sharing platforms have various limitations, such as:

• documents have to be uploaded to a supplier’s server, which is not under your control.
• documents are generally viewed via a browser, so there is limited screen-grabbing prevention (if any) and limitations on the controls you can enforce.
• printing to PDF or other file drivers is not prevented, so users can save documents locally to disk if you allow printing.
• users must always be online to view and print documents.
• users can share their login credentials with others without being detected.
• controls can be bypassed by users editing or disabling JavaScript in the browser.  A good example of this is Google Docs Security.
• pricing is usually based on the number of user accounts and/or documents and can get expensive quite quickly. In other cases, you pay for each GB of storage, which can quickly become pricey for big files.

Secure document sharing platforms such as Microsoft Azure Rights Management have mainly evolved from document collaboration systems or internal document sharing solutions. They often have complex role-based permissions, which are best suited to internal use.  Admins must define formal access control structures (i.e., there is no concept of selling the documents and controlling their actual use).

However, most of the documents you need to share securely go beyond the concepts of collaboration (e.g., distributing reports, hipaa, finance information, formal board minutes, formal procedures, etc.). In certain countries with poor internet connections, users still need to store and view files offline, while other use cases require a local, up-to-date backup. While some cloud services allow you to sync to a local device, this introduces additional problems. Controls are not usually maintained, while there is a risk of interception by hackers and poor version control.

Most importantly, however, companies need to decide whether they want to store their files on someone else’s internet-accessible server.  A server that could experience outages or even be hacked, and the documents extracted.  Even if a secure document sharing platform is right for you, it may be necessary to find a solution where you maintain control of the files and don’t ‘give’ them to the security provider.

   Internal document sharing solutions

It is naturally much easier to stop sharing over infrastructure that is under your control. There are a few options for internal document sharing solutions, such as:

• Internal secure file-sharing platforms such as SharePoint
• Data loss prevention tools
• Rights management controls

However, these options are still not infallible. It’s difficult to stop employees from sharing with unauthorized third parties and departments, particularly when you have a partially remote workforce or need to communicate with select outside parties. As we have covered in Why SharePoint is not secure, it is based on ACL permission, which provides limited control over how users can use documents, not preventing copy and paste or printing. Additionally, it is easy to give wrong access by mistake due to the complexity of permissions.

Data loss prevention tools focus primarily on stopping sensitive information from leaving the premises. They monitor networks and emails in a bid to prevent leaks, and this is usually only partially successful. They rely on the accurate detection of key phrases and file formats, as well as good groundwork by IT admins in classification and marking. It is generally good at preventing accidental leaks but poor at preventing threat actors from exfiltrating data. Of course, it is also useless at stopping authorized third parties from leaking because your DLP solution has no visibility over their network.

Most internal rights management controls rely on basic read/write/access functions, which fail to stop determined individuals from sharing content. For instance, they typically do not prevent screenshots, a prevalent method of information sharing. In certain situations, like with Microsoft RMS, users can entirely bypass protection using freely accessible tools.

  Encrypted file sharing services

Encrypting a document is fine if your objective is to secure the file at rest – i.e. you want to store documents securely either locally or in cloud storage.  Cryptography can also be useful in transit when you’re sending a file to another user by email etc. and want to be sure that anybody who intercepts the email will not be able to read it.

Document encryption, however, has its limits.  Once a file is decrypted, there are no access controls governing its use.  If you send an encrypted document to another user – because you only want them to be able to view it – there is nothing to prevent them from sending the decrypted document to anyone they choose.  In other words, it only provides protection if you trust the receiver completely.  This is especially important to remember if you are selling documents such as reports, ebooks, etc., and want to ensure that only those who have paid for them can use them.  Controlling usage is also key if you have confidential company information that must only be made available to specific employees, board members, or third parties.

  Sharing documents securely using DRM security

DRM adds a complementary layer of security to document encryption. With DRM, files are encrypted to protect them in transit and at rest, and then access and other controls are added to govern use. Core controls prevent copying and document modification, stop or limit printing, and stop screen-grabbing by preventing print screens and the use of screen-grabbing tools.

To prevent unauthorized sharing, DRM systems use licensing controls to tie users and their devices to specific documents.  This ensures the owner can share them securely amongst only intended recipients (unless of course, an authorized recipient is willing to give their tablet device, mobile phone, or laptop to someone else).  Many DRM systems also provide dynamic document watermarking – user details are displayed on a document when it is viewed and printed to discourage photographs of the screen, or if printing is allowed, to discourage printed distribution.  Adding watermarks dynamically ensures the document only needs to be protected once, rather than once for every single user.

More DRM systems enable documents to be shared securely in only authorized locations by limiting use to specific countries and IP address ranges.  This ensures that users using mobile devices cannot open secure documents outside an office location or in countries where usage is forbidden due to regulations.

  Secure self-destruct file sharing: sharing documents securely for limited time periods

Another advantage of using document DRM systems to share documents securely is the ability to automatically expire and revoke document use after a certain amount of time (self-destruct file sharing).  This could be after a number of views or prints, a number of days, or on a fixed date.  Ensuring information can no longer be viewed after a certain period is especially useful for M&A documents, where information is only required for a limited period, or for documents that have a natural life span.  See PDF expiry.

DRM systems also allow users to instantly revoke access to documents regardless of where they are stored. If the information has been published by mistake, access has been given to the wrong person, or a chargeback has been made, you can instantly recall it.

  Sharing documents securely with accountability – track & log document use

When sharing documents securely, it may be important to establish that an authorized user has viewed and/or printed a document, whether this is for legal/compliance reasons or to help identify leaks. DRM systems can help here by tracking document use and providing log files detailing when documents were opened and printed, by whom, and when this occurred.

  Conclusion: How to share documents securely

When sharing documents securely, there are many issues that have to be considered.

1. What kind of document control are you seeking to exert – internal use, internal and external, or purely external?
2. Do you trust the recipients enough to know that they will not pass documents on?  How much control do you want over your files when dealing with untrusted parties?  Do you trust a “secure file-sharing” company to protect and host your confidential or valuable documents on their servers?  Do users always have an Internet connection available, and how much security is enough?
3. Do you need to log users’ activities? Are you licensing the use of information content rather than sharing files at a peer-to-peer level?

For the simpler requirements, a collaboration system may offer enough controls – documents are in a constant state of flux.  As you transition to selling documents or the distribution of private documents to remote environments where bespoke security is required, DRM is essential to maintain document content protection.