SharePoint Online and OneDrive for Business – Preventing external sharing of data

A recent (September 2017) article suggested that OneDrive for Business (ODfB) (and by extension SharePoint Online (SPO); ODfB is a SharePoint-based service), a key application in Office 365 was a potential source of data leaks and/or target for hacking attacks.

I don’t disagree that, if not configured correctly, any online document management system – not just ODfB/SPO – could be the source of leaks or the target of external attacks. Especially if these systems, and the security controls that can protect the data in them, are not properly configured, governed, administered, and monitored.

But, I would ask, what controls do most organisations have in place now for documents stored in file shares and personal file folders, not to mention USB sticks, and the ability to send document via Bluetooth to mobile devices or upload corporate data to third-party document storage systems? Probably not many, because users have no other way to access the data out of the office.

As we will see, the controls available in Office 365 are likely to be more than sufficient to allow users to access to their documents out of the office, while at the same time reducing (if not eliminating) the sharing of documents with unauthorised users.

How to stop or minimise sharing from OneDrive for Business and SharePoint Online

There is one simple way to prevent the sharing of data stored in SPO and ODfB with external people – don’t allow it.

There are several ways to control what can be shared, each allowing the user a bit more capability. All these options should be based on business requirements and information security risk assessments, and Office 365 configured accordingly.

In this article I will start with no sharing allowed, and then show how the controls can be reduced as necessary.

External sharing – on or off

This is the primary setting, found in the main Office 365 Admin centre under Settings > Services & add-ins > Sites. If you turn this off, no-one can share anything stored in SPO or ODfB.

The option is shown below:

If you do allow sharing, you need to decide (as shown above) if sharing will be with:

• Only existing external users
• New and existing external users [Recommended]
• Anyone, including anonymous users

The second option is recommended because it doesn’t restrict the ability to share with new users. The last option is unlikely to be used in most organisations and comes with some risks.

The next place to set these options are in the SPO and ODfB Admin centres.

OneDrive admin center

If the previous option is enabled, the following options are available for ODfB. Note that BOTH SharePoint and OneDrive are included here because the latter is a part of the SharePoint environment.

• Let users share SharePoint content with external users: ON or OFF.
  • NOTE: If this option is turned OFF, all the following options disappear.
• If sharing with external users is enabled, the following three options are offered:
  • Only existing external users
  • New and existing external users [Recommended]
  • Anyone, including anonymous users
• Let users share OneDrive content with external users: ON or OFF
  • This setting must be at least as restrictive as the SharePoint setting.
• If sharing with external users is enabled, the following three options are offered
  • Only existing external users
  • New and existing external users [Recommended]
  • Anyone, including anonymous users

If sharing is allowed, there are three sharing link options:

• Direct – only people who already have permission [Recommended]
• Internal – only people in the organisation
• Anonymous access – anyone with the link

You can limit external sharing by domain, by allowing or blocking sharing with people on selected domains.

External users have two options:

• External users must accept sharing invitations using the same account that the invitations were sent to [Recommended]
• Let external users share items they don’t own. [This should normally be disabled]

A final ‘Share recipients’ checkbox allow the owners to see who viewed their files.

SharePoint admin center

The SPO admin center (to be upgraded in late 2017) has two options for sharing.

The first option is under the ‘sharing’ section which currently has the following options:

Sharing outside your organization

Control how users share content with people outside your organization.

• Don’t allow sharing outside your organization
• Allow sharing only with the external users that already exist in your organization’s directory
• Allow users to invite and share with authenticated external users [Recommended]
• Allow sharing to authenticated external users and using anonymous access links

Who can share outside your organization

• [Checkbox] Let only users in selected security groups share with authenticated external users

Default link type

Choose the type of link that is created by default when users get links.

• Direct – only people who have permission [Recommended, same as above]
• Internal – people in the organization only
• Anonymous Access – anyone with the link

Default link permission

Choose the default permission that is selected when users share. This applies to anonymous access, internal and direct links.

• View [Recommended]
• Edit

Additional settings (Checkboxes)

• Limit external sharing using domains (applies to all future sharing invitations). Separate multiple domains with spaces.
• Prevent external users from sharing files, folders, and sites that they don’t own [Recommended]
• External users must accept sharing invitations using the same account that the invitations were sent to [Recommended]

Notifications (Checkboxes)

E-mail OneDrive for Business owners when

• Other users invite additional external users to shared files [Recommended]
• External users accept invitations to access files [Recommended]
• An anonymous access link is created or changed [Recommended]

Sharing via the Site Collections option

In addition to the options above, sharing options for each SharePoint site are set in the ‘site collections’ section as follows. Note that the default is ‘no sharing allowed’. A conscious decision must be taken to allow sharing, and what type of sharing.

When a site collection name is checked, the following options are displayed.

Sharing outside your company

Control how users invite people outside your organisation to access content

• Don’t allowing sharing outside your organisation (default)
• Allow sharing only with the external users that already exist in your organization’s directory
• Allow external users who accept sharing invitations and sign in as authenticated users
• Allow sharing with all external users, and by using anonymous access links

If anonymous access is not permitted (setting above), a message in red is displayed:

Anonymous access links aren’t allowed in your organization

SharePoint Sharing option

The SharePoint Admin Centre has an additional ‘Sharing’ section with the same settings as shown above for ODfB. It is expected that these multiple options will be merged in the new SharePoint Admin Centre due for release in late 2017.

Additional security controls

In addition to all the above settings, there are a range of additional controls available:

• All user activities related to SPO and ODfB, including who accessed, viewed, edited, deleted, or shared files is accessible in the audit logs.
• SPO and ODfB content may be picked up by Data Loss Prevention (DLP) policies and users prevented from sending them externally. This is of course subject to the DLP policies being able to identify the content correctly.
• SPO and ODfB content may be subject to records retention policies set by preservation policies. These may impact on the ability to send documents externally.
• SPO and ODfB content may be subject to an eDiscovery case.
• Administrators can be notified when users perform specific activities in both SPO and ODfB.
• Sharing (and access to the documents once shared) may be subject to security controls enforced through Microsoft Information Protection.

Conclusion

In summary, the settings above allow an organisation to strongly control what can be shared. If sharing is allowed, certain additional controls determine whether the sharing is for internal users or for users external to the organisation. If the latter is chosen, there are further controls on what external users can do. Audit controls and policies may also control how users can share information externally.

The key takeaway is that organisations should ensure that the sharing options available in Office 365 are based on the organisation’s business requirements and security risk framework.

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Office 365 & SharePoint Online – Data Loss Prevention (DLP)

Summary

Office 365 includes a range of information security and protection capabilities. This post focusses on the configuration and implementation of Data Loss Prevention (‘DLP’) capabilities in SharePoint Online and OneDrive for Business (ODfB).

Note: Microsoft have advised that the Office 365 DLP framework will apply to both Exchange and SharePoint/ODfB in the near future. For Exchange settings see https://technet.microsoft.com/en-us/library/jj200706(v=exchg.150).aspx and https://technet.microsoft.com/en-us/library/jj150527(v=exchg.150).aspx for more information.

Purpose of DLP

The purpose of DLP is to protect specific and definable types of sensitive company or agency information by preventing (or monitoring) its deliberate or inadvertent exfiltration from the organisation.

Examples of exfiltration methods where DLP can be used include:

• Attachments to emails.
• Uploads to web-based systems.

Examples of the types of sensitive information that can be protected with DLP include:

• Financial data. For example, bank account numbers, tax file numbers, credit/debit card numbers.
• Personal and sensitive information (PSI). For example, driver’s licence numbers, tax file numbers, passport numbers.
• Medical and Health records. For example, medical account numbers.

The requirement to protect sensitive information is the subject of legislation in a number of countries.

Enabling Data Loss Prevention in Office 365

DLP in Office 365 enabled through policies that are set in the Security and Compliance Admin Centre of the Office 365 Admin Portal, under ‘Threat Management’ > ‘Data Loss Prevention’.

DLP policies are set by the Office 365 Global Administrator, as well as the Compliance Administrator and/or the Security Administrator if these roles have been configured in the Security and Compliance Admin Centre.

To create a DLP policy, the Administrator clicks on the + icon in the Data Loss Prevention screen. This opens a new window with the following options displayed.

A custom policy is one that is defined by the organisation. It would normally be for content that contains specific values.

The options ‘Financial regulations’, ‘Medical and health regulations’, and ‘Privacy regulations’ include default Microsoft-provided policies. Each of these default policies includes a description, coverage (e.g., what information is protected), and where the information is to be protected (e.g., in SharePoint Online, OneDrive for Business, and Exchange Online).

Enabling and modifying default policies

After selecting a default policy, the authorised user must then identify the services that may store the information that need to be protected – SharePoint Online, OneDrive.

Note: The option to choose Exchange Online is (as of 13 March 2017) still unselectable.

The next option allows the Administrator to customise the rule that has been chosen. If a default policy has been selected in the previous dialog, options for that policy will display; these may include ‘count sensitivity’ (i.e., how many times the sensitive content is identified. Low count means high sensitivity to sensitive content.

The Administrator may add a new rule or edit one of the default options.

The Administrator may modify the conditions, actions and what happens when there is an incident for each of the default policies – see below for further details.

Defining custom DLP policies

If a custom policy is required, the Administrator clicks on ‘Custom Policy’ from the ‘Data Loss Prevention’ opening dialog screen, and then ‘Next’ at the bottom of the screen. The Administrator must define which services are to be protected (same as for default policies, above).

The next screen allows the Administrator to create a new policy, via the + icon.

In the new window that opens, the Administrator can then must define the new DLP rule through Conditions, Actions, Incident reports and General.

Conditions, Actions, Incident reports, General options

For either default or custom policies, the Administrator must set the following rules:

• Conditions – what will cause the policy to run?
• Actions – what will happen when the policy runs?
• Incident reports – how is reporting managed?
• General – any other points.

Conditions

For default policies, conditions are pre-defined and are based on (a) the type of content (e.g., credit card numbers, bank account numbers) and (b) whether the content is shared internally or externally.

These pre-defined conditions may be removed or edited, and new conditions may be added. Editing options include the number of times the sensitive content is found (‘Min count’, ‘Max count’), and both maximum and minimum percentage-based ‘confidence levels’.

For custom policies, the Administrator must define which conditions are to be met:

• If you choose ‘Content contains sensitive information’, you must define the information through a + option. This brings up all the default choices provided by Microsoft.
• If you choose ‘Content is shared with’, it allows you define if the information is shared with people inside or outside the organisation.
• If you choose ‘Document properties contain any of these values’, you must define the values that would be found in a document. Note that, if this option is selected, the property must be configured in the SharePoint Online search settings.

Actions

For default policies, the actions to be taken are pre-defined and are based on sending a notification.

For custom policies, the Administrator must first decide whether the action will be to (a) block the content or (b) send a notification.

If ‘Block the content’ is selected the user will be unable to send an email or access the shared content.

If ‘Send a notification’ is selected it offers the same options as for custom policies. Note the ability to customise the email notification.

Incident Reports

When ‘Incident Reports’ is selected for both custom and default policies, the following options are available. Incident reports should be sent to the Administrator/s.

General

Default policies are pre-named but the name can be modified. This is also where the policy can be disabled.

Custom policies must be named and a decision made whether to enable it, test it, or turn it off. As noted below it is possible to test the policy first, to collect data.

DLP Reporting

Reporting from the DLP policies is accessed from the Security and Compliance Centre > Reports > Dashboard.

Applying information security and protection capabilities in Office 365 & SharePoint Online

Office 365 includes a range of information security and protection capabilities. These capabilities are first set in Azure and then applied across the Office 365 environment, including in Exchange and SharePoint Online. This post focuses on the application of these capabilities and settings to SharePoint Online.

Enterprise E3 and E4 plans include the ability to protect information in Office 365 (Microsoft Exchange Online, Microsoft SharePoint Online, and Microsoft OneDrive for Business). If you don’t have one of those plans you will need a subscription to Microsoft Azure Rights Management.

Enabling Information Protection in Azure

The following steps must be carried out the first time Information Protection is enabled on Azure:

• Log on to Azure (as a Global Administrator).
• On the hub menu, click New. From the MARKETPLACE list, select Security + Identity.
• In the Security + Identity section, in the FEATURED APPS list, select Azure Information Protection.
• In the Azure Information Protection section, click Create.

This creates the Azure Information Protection section so that the next time you sign in to the portal, you can select the service from the hub ‘More Services’ list.

Default Azure Information Protection policies

There are four default levels in Azure Information Protection:

• Public
• Internal
• Confidential
• Secret

Once set, these levels can be applied as labels to information content. Sub-labels and new labels may also be created, as necessary via the ‘+ Add a new label’ option.

The configuration settings are shown below:

Each of these label/level settings may:

• Be enabled or disabled
• Be colour-coded
• Include visual markings (the ‘Marking’ column)
• Include conditions
• Include additional protection settings.

Each includes a suggested colour and recommended tip, which are are accessed via the three dot menu to the right of each label.

Markings

When selected, this option will place a label watermark text on any document when the label is selected.

Conditions

Conditions may be applied, for example, if credit card numbers are detected in the text. It allows the organisation to define how conditions apply, how often (Occurrences), and whether the label would be applied automatically or is just a recommended option.

Global Policy Settings

In addition to the settings per level, there are three global policy settings:

• All documents and emails must have a label (applied automatically or by users): Off/On
  • When set to On, all saved documents and sent emails must have a label applied. The labeling might be manually assigned by a user, automatically as a result of a condition, or be assigned by default (by setting the Select the default label option).
• Select the default label:
  • This option allows the organisation the default label to be be assigned to documents and emails that do not have a label.
  • Note: A label with sub-labels cannot be set as the default.
• Users must provide justification to set a lower classification label, remove a label, or remove protection: Off/On [Not applicable to sub-labels]
  • This option allows you to request user justification to set a lower classification level, remove a label, or remove protection. The action and their justification reason is logged in their local Windows event log: Application > Microsoft Azure Information Protection.

Custom Site

A custom site may be set up for the Azure Information Protection client ‘Tell me more’ web page.

Unique ‘Scoped’ Policies

In addition to the default policies listed above, a unique policy may be created. These are called Scoped Policies.

Enabling (and Disabling) Azure Information Protection

The steps above are used to set up the labels. They must then be enabled to provide protection. The steps below also allow protection to be removed.

From the Azure Information Protection section, click on the label to be set, then click on Protect. This action opens the Permission settings section.

Select Azure RMS and ‘Select template’, and then click the drop down box and select the default label template. This will probably show as, e.g., ‘(Your Company Name) – Confidential’.

Click ‘Done’ to enable this label and repeat for the others.

Note: If a new template is created after the Label section is opened, you will need to close this section and return to step 2 (to select the label to change), so that the newly created template is retrieved from Azure.

Removing Protection

Users must have the appropriate permissions to remove Rights Management protection to apply a label that has this option. This option requires them to have the Export (for Office documents) or Full Control usage right, or be the Rights Management owner (automatically grants the Full Control usage right), or be a super user for Azure Rights Management. The default rights management templates do not include the usage rights that lets users remove protection.

If users do not have permissions to remove Rights Management protection and select this label with the Remove Protection option, they see the following message: Azure Information Protection cannot apply this label. If this problem persists, contact your administrator.

Additional notes

If a departmental template is selected, or if onboarding controls have been configured:

• Users who are outside the configured scope of the template or who are excluded from applying Azure Rights Management protection will still see the label but cannot apply it. If they select the label, they see the following message: Azure Information Protection cannot apply this label. If this problem persists, contact your administrator.
• All templates are always shown, even if a scoped policy only is configured. For example, a scoped policy for the Marketing group; the Azure RMS templates that can be selected will not be restricted to templates that are scoped to the Marketing group – it is possible to select a departmental template that selected users cannot use. It is a good idea (to help troubleshoot issues later on) to name departmental templates to match the labels in the scoped policy.

Once these settings are made, they need to be published (via the ‘Publish’ option) to become active.

Enabling Information Protection in Office 365

Activating Information Protection in the Office 365 Admin Portal

Once they have been configured and published, it is then necessary to enable the required settings in the Office 365 Admin Portal (Settings > Services & add-ins > Microsoft Azure Information Protection).

To do this, log on to the Office 365 Admin Portal (as a Global Administrator) then click on ‘Services & add-ins’ under Settings. Click ‘Activate’ to activate the service.

Activating Information Protection for Exchange and SharePoint Online

Once the service is activated for Office 365, it can then be activated in the Exchange and SharePoint Admin Centres. In SharePoint Online this is done via the Admin Center section ‘Settings’ and ‘Information Rights Management (IRM)’.

Configuring SharePoint and SharePoint Libraries for IRM

As at 12 March 2017, it is only  possible to link Azure Information Protection classification policies with SharePoint Online if a new site is created via the SharePoint end user portal, as it appears as an option when enabled. Sites created via the SharePoint Admin Portal do not (yet) include the option to apply a protection classification.

If the creation of sites via the SharePoint end user portal is enabled, users with appropriate permissions (e.g., Owners with Full Control) can apply Information Rights Management to SharePoint libraries in their sites.

IRM is enabled on each individual library or list where the settings will be applied via Library Settings > Information Rights Management, under Permissions and Management.

Check the box to ‘Restrict permissions on this library on download’. Only one policy can be set per library.

Assigning Information Protection labels to Office documents

[NOTE: for clients that have installed versions of Office, the Azure Information Protection client needs to be installed on the desktop. See this site for more information: https://docs.microsoft.com/en-us/information-protection/get-started/infoprotect-tutorial-step3%5D

When labels are configured and enabled, they can then be be automatically assigned to a document or email. Or, you can prompt users to select the label that you recommend:

• Automatic classification applies to Word, Excel, and PowerPoint when files are saved, and apply to Outlook when emails are sent. It is not possible to use automatic classification for files that were previously manually labeled.
• Recommended classification applies to Word, Excel, and PowerPoint when files are saved.

Applying the policies to Exchange and office

The site below describes how to apply these policies to Exchange and Office applications. These are not discussed further here.

https://github.com/Microsoft/Azure-RMSDocs/blob/master/Azure-RMSDocs/deploy-use/configure-applications.md

Information Security in SharePoint Online

Until now, the security of information stored in SharePoint on-premise implementations was largely based on access control groups that gave or restricted access to the content on the site. Access to the content, and ability to do anything with it (e.g., edit, read) depending on what group you belonged to. The main five access control groups are:

• SharePoint Administrator/s: Access to everything.
• Site Collection Administrator: (Usually) access to everything, but this can be disabled.
• Site Owners: ‘Full Control’ access to everything (except for the Site Collection Administration elements in Site Settings).
• Site Members: ‘Contribute’ or add/edit access.
• Site Visitors: Read only.

Other groups such as Designer and Reader existed for specific purposes.

At any point from the top level Site Collection downwards through all the content, these inherited permissions could be stopped and unique permissions – including for both individuals and new access groups – could be created and applied to control access to content.

Audit logs supplemented access controls by providing details of who did (including changing security permissions) or accessed what, and when. While the SharePoint Administrator and Site Collection Administrator’s names are not visible to Site Owners, Members or Visitors, they appear in the audit logs if any activity is recorded. System account activity is also recorded in the logs.

New Security Controls in SharePoint Online

SharePoint Online brings a range of new options to protect the security of information, in addition to access controls. These options, some of which are included with SharePoint 2013 an onwards, are:

• Information security classifications
• Data Loss Prevention (DLP)
• Audited sharing
• Information Rights Management (IRM)
• Shredded storage (new from SP 2013)

Two of these options can be seen in the following Microsoft diagram:

Source: ‘Monitoring and protecting sensitive data in Office 365’ https://msdn.microsoft.com/en-us/library/mt718319.aspx

Information Security Classifications

According to a number of online sources, from at least March 2011, Microsoft has classified its own information into three categories: High Business Impact (HBI), Moderate Business Impact (MBI), and Low Business Impact (LBI).

• High Business Impact (HBI): Authentication / authorization credentials (i.e., usernames and passwords, private cryptography keys, PIN’s, and hardware or software tokens), and highly sensitive personally identifiable information (PII) including government provided credentials (i.e. passport, social security, or driver’s license numbers), financial data such as credit card information, credit reports, or personal income statements, and medical information such as records and biometric identifiers.
• Moderate Business Impact (MBI): Includes all personally identifiable information (PII) that is not classified as HBI such as: Information that can be used to contact an individual such as name, address, e-mail address, fax number, phone number, IP address, etc; Information regarding an individual’s race, ethnic origin, political opinions, religious beliefs, trade union membership, physical or mental health, sexual orientation, commission or alleged commission of offenses and court proceedings.
• Low Business Impact (LBI): Includes all other information that does not fall into the HBI or MBI categories.

Source: ‘Microsoft Vendor Data Privacy – Part 1’ (March 2011) https://www.auditwest.com/microsoft-vendor-data-privacy/

Microsoft released code (via Github) to apply these classifications to SharePoint on-premise deployments in 2014.

Source: https://github.com/OfficeDev/PnP/tree/master/Solutions/Governance.TimerJobs

In 2016 Microsoft released a Technical Case Study highlighting how it migrated all its SharePoint content to SharePoint Online – and how information classification formed part of that process.

Source: ‘SharePoint to the Cloud – Learn how Microsoft ran its own migration’ (Case Study – 2016)  https://msdn.microsoft.com/en-us/library/mt668814.aspx

In May 2016, Microsoft announced that this form of classification would be added to new SharePoint Online site collections during 2016.

The application of security classifications to SharePoint Online sites has two elements:

• Security and compliance policies, set by the SharePoint Administrator via either the ‘Security policies’ or ‘Data management’ section of the Office 365 Security & Compliance Center. [As of 23 May 2016 the only policies are ‘Device management’ and ‘Data Loss Prevention’. While the DLP policies appear to allow the inclusion of security classifications, it is expected that Microsoft will add more options to support the application of security classifications during 2016. See below for more information on DLP.]
• A new drop-down, three choice (LBI, MBI, HBI) option in the ‘Start a new site’ dialogue box under the question ‘How sensitive is your data?’ The choice of classification invokes the relevant security and compliance policies.

Microsoft provides examples of the types of information that would be covered by each of these at this interactive site: https://www.microsoft.com/security/data/

The application of these policies will enable organisations to control what happens to information stored in sites assigned these classifications. Among other things, this can prevent users from sending (or trying to send) MBI or HBI classified information to people not allowed to receive or view it, including through DLP policies discussed in the next section.

Data Loss Prevention (DLP)

Data Loss Prevention policies allow organisations to:

• Identify sensitive information across both SharePoint Online and OneDrive for Business sites (and in Exchange, through the same settings).
• Prevent the accidental sharing of sensitive information, including information classified MBI or HBI.
• Monitor and protect sensitive information in the desktop versions of Word, Excel and Powerpoint 2016.
• Help users learn how to stay compliant by providing DLP tips.
• View reporting on compliance with policies.

 

DLP Conditions

DLP works by giving Site Administrators the ability to create and apply DLP policies in the Security & Compliance Center for SharePoint (which includes OneDrive for Business; there is a separate Center for Exchange). In the Center, the Administrator navigates from ‘Security policies’ to ‘Data loss prevention’.

The DLP policy area includes a range of ‘ready-to-use’, financial, medical and privacy templates for a number of countries including the US, UK and Australia. Examples of pre-defined Australian sensitive information types include: bank account numbers, driver’s licence numbers, medical account numbers, passport numbers, and tax file numbers.

You may also create a custom DLP policy.

Sources: https://technet.microsoft.com/en-us/library/ms.o365.cc.newpolicyfromtemplate.aspx  https://support.office.com/en-gb/article/Send-notifications-and-show-policy-tips-for-DLP-policies-87496bc5-9601-4473-8021-cb05c71369c1

DLP Actions

Specific actions must be set for every DLP policy; that is, what happens if the policy conditions are met. The default actions are:

• Block access to content (for everyone except its owner, the person who last modified the content, and the owner of the site where the content is stored AND send a notification by email.
• Suggest a Policy Tip to users. Options are (a) Use the default Policy Tip or (b) Customise the Policy Tip.
• Allow override options. There is one main checkable option (‘Allow people who receive this notification to override the actions in this rule’) and two sub options:
  • A business justification is required to override this rule, and
  • A false positive can override this rule.

In addition to these actions, where the DLP policy identifies sensitive content in a document stored in SharePoint Online or OneDrive for Business it displays a small warning ‘stop’ sign icon on the document icon. Hovering over the item displays information about the DLP policy and options to resolve it.

DLP Incident Reports

Incident reports are designed to alert a compliance officer to details of events triggered by the DLP conditions, and provide reporting on those events.

Sources:

https://technet.microsoft.com/en-US/library/ms.o365.cc.DLPLandingPage.aspx

Audited Sharing

Information sharing is a common activity in SharePoint and in SharePoint 2016 and SharePoint Online it is actively encouraged through a new Share option.

In addition to other existing audit options, sharing activity can now be audited in SharePoint Online. The audit logs for Office 365 (which must be enabled) are accessed through the Office 365 Admin Center > Security & Compliance Center > Search & investigation > Audit log search.

Source: https://support.office.com/en-us/article/Use-sharing-auditing-in-the-Office-365-audit-log-50bbf89f-7870-4c2a-ae14-42635e0cfc01?ui=en-US&rs=en-US&ad=US]

Information Rights Management (IRM)

Microsoft’s Information Rights Management capability provides an additional layer of protection for a number of document types at the list and library level in SharePoint Online sites.

Supported document types include PDF, the 97-2003 file formats for Word, Excel and PowerPoint (e.g., Office documents without the ‘x’ at the end of the file extension – ‘word.doc’, the Office Open XML formats for Word, Excel, and PowerPoint (e.g. with the ‘x’ at the end – ‘word.docx’), the XML Paper Specification (XPS) format.

According to Microsoft, IRM:

‘… enables you to limit the actions that users can take on files that have been downloaded from lists or libraries. IRM encrypts the downloaded files and limits the set of users and programs that are allowed to decrypt these files. IRM can also limit the rights of the users who are allowed to read files, so that they cannot take actions such as print copies of the files or copy text from them.’

IRM is enabled via the Office 365 Admin Center > Admin > SharePoint > Settings > Information Rights Management > ‘Use the IRM service specific in your configuration’ and then ‘Refresh IRM Settings’.

Image source: ‘Apply IRM to a List or Library’ https://support.office.com/en-us/article/Apply-Information-Rights-Management-to-a-list-or-library-3bdb5c4e-94fc-4741-b02f-4e7cc3c54aa1

 

When IRM is activated on a library, any file that is downloaded is encrypted so that only authorised people can view them. Again, according to Microsoft:

‘Each rights-managed file also contains an issuance license that imposes restrictions on the people who view the file. Typical restrictions include making a file read-only, disabling the copying of text, preventing people from saving a local copy, and preventing people from printing the file. Client programs that can read IRM-supported file types use the issuance license within the rights-managed file to enforce these restrictions. This is how a rights-managed file retains its protection even after it is downloaded.’

Source:

https://support.office.com/en-us/article/Set-up-Information-Rights-Management-IRM-in-SharePoint-admin-center-239ce6eb-4e81-42db-bf86-a01362fed65c

Shredded storage

Shredded storage, as the name suggests, describes the way documents are stored in SharePoint, starting from SharePoint 2013. Instead of storing a document as a single blob, documents are stored in multiple blobs.

This is a more efficient – and possibly more secure – way to manage documents when they are updated by only updating the element/s that were changed. According to a Microsoft presentation on 4 May 2016:

‘… every file stored in SharePoint is broken down into multiple chunks that are individually encrypted. And, the keys are stored separately to keep the data safe. In the future, we would like to give you the ability to manage and bring your own encryption keys that are used to encrypt your data stored in SharePoint. If you want, you can revoke our access to the keys. And we will not be able to access your data in the service’.

Source:

https://blogs.technet.microsoft.com/wbaer/2012/11/12/introduction-to-shredded-storage-in-sharepoint-2013-rtm-update/

Other Information Security related options

The Microsoft website ‘Monitoring and protecting sensitive data in Office 365’ provides further information about other Information Security options in Office 365, including reporting options to support auditing of activity in the tenant.

Source: https://msdn.microsoft.com/en-us/library/mt718319.aspx