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Web App Content Security for Office 365

Office 365
by Ben Chai
, 08 May 2012

Privacy and integrity of content is an essential component for storing confidential information in the Cloud.  As such, Microsoft Office 365 supports an integral array of security settings to help protect content from unauthorised access via the on-premise versions of the Office applications.

To access these security settings, users would need to:

  1. Click on the File Menu
  2. Select Info
  3. Click on the drop down arrow at the bottom right of the Protect button

Word, Excel and PowerPoint contain four main security settings:-

  • Mark as Final which sets the document, spreadsheet or presentation to read-only. Although Mark as Final does not prevent unauthorised access, it is useful to prevent accidental over-writing and changes to the original content. However, any user can change this setting by clicking on the Edit Anyway button shown when they access the data.
  • Encrypt with Password is useful to protect content integrity and confidentiality. As of writing, one of the strongest encryption algorithms, 128-bit AES, is used – however strong algorithms alone are not enough to defeat the variety of password recovery and cracking tools available without the use of complex passwords and passphrases.
  • Restrict Permission by People (or Information Rights Management) is useful when a user wishes to select who can read, print or edit the content. If a person is not in this list then they cannot view the data.
  • Add a Digital Signature is useful to ensure the integrity of the content of a file and throw up a flag should an unauthorised change be made. Once content has been signed with a digital signature, users will be able to verify (a) the person who signed the content, (b) the date and time the content was signed, and (c) if the content has been altered since it was originally signed

Microsoft Excel has two additional security settings; Protect Current Sheet and Protect Workbook Structure.

  • Protect Current Sheet provides greater granularity to the security of spreadsheet editing compared to the Restrict Permission by People option. The Allow Edit component of the Restrict Permission by People option gives complete edit access to a spreadsheet whereas Protect Current Sheet can password protect and lock individual cells, rows and columns.
  • Protect Workbook Structure prevents other users from changing the architecture of a workbook, for example preventing the addition or deletion of spreadsheets to the workbook.

Microsoft Word has one additional security setting to the main four, Restrict Editing.  Restrict Editing enables users to restrict the type of formatting changes that can be made within the document.  For example, if the document is a lengthy proposal, then all formatting can be prevented apart from editing made in tracked changes.

These security settings are an integral component of the Office 365 suite to help users protect the privacy and integrity of their content and as such high security documents can only be edited via the on-premise versions of Office i.e. you cannot use Web Apps to edit them. A step by step guide on how to restrict people by permission can be read in the article on Information Rights Management.

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