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Data Loss Prevention Strategies for Microsoft Exchange Server. In today’s digital landscape, safeguarding sensitive information within Microsoft Exchange Server is paramount. This article explores effective data loss prevention (DLP) strategies for Microsoft Exchange Server environments. Uphold the confidentiality, integrity, and availability of your data by addressing the potential risks associated with data breaches and unauthorized disclosure. Attain this goal through the implementation of proactive measures and the efficient utilization of existing capabilities.

Data Loss Prevention Strategies for Microsoft Exchange Server

Emails as reliable medium for business communication they often contain sensitive or confidential data or information we don’t want to leak outside the organization. Thus, it’s essential to define mail flow policies to ensure fair usage of the organization’s messaging system and protect sensitive information. 

Data Loss Prevention (DLP) Overview

Sensitive information cannot be lost, misused, or accessed by unauthorized users thanks to a collection of procedures and technologies known as data loss prevention, or DLP.

Data Loss Prevention Software

Driven by regulatory compliance requirements ( HIPAA, PCI-DSS, or GDPR). DLP software classifies regulated, confidential, and business-critical data and identifies violations of regulations specified by businesses or within a predetermined policy pack.

Upon detecting, DLP implements corrective measures such as encryption, notifications, and other safeguards to stop end users from inadvertently or intentionally disclosing information. 

To safeguard data in use, in transit, or at rest, data loss prevention software and applications filter data streams on corporate networks, monitor endpoint activity, and monitor data in the cloud. In addition, DLP offers reporting to satisfy auditing and compliance needs and pinpoint anomalies and weak points for forensics and incident response.

DLP remediates various pain points, including insider threats, Office 365 data security, user and entity behaviour analysis, and advanced threats. This article focuses more on Microsoft Exchange data loss prevention policies.

Data Loss Prevention (DLP) policies in Exchange Server are collections of mail flow rules that help Exchange or IT administrators filter email messages and protect sensitive information. DLP policies contain specific conditions, exceptions, and actions to detect and filter email messages, attachments, or other mail items based on the content. This process helps avoid data leakage outside the organization or corporate network.

It protects the Exchange database from malicious emails or attachments that causes Exchange database corruption or result in a ransomware attack. DLP is an inbuilt premium feature in on-premises Exchange Server 2013 and later versions, available only with an Exchange Enterprise Client Access License (CAL). Before Exchange 2013, there were transport rules to detect and filter incoming and outgoing messages. However, they were meant for simple searches and needed to be more reliable.

DLP continuously monitors (checks & scans) incoming and outgoing email contents based on keywords, regular expressions, or dictionaries to identify whether the message contains sensitive or non-sensitive information and early signs of ransomware. We may also use the document fingerprinting feature to define or create DLP policies for detecting sensitive information or malicious emails/ransomware in emails or attachments with unique patterns or file extensions.

One of the best features of DLP is that once defined, it detects and displays Policy Tips to the user that they might be violating the policy before sending the email containing sensitive information. We enforce DLP policies to ensure our organization meets local, national, or international data security and regulatory compliances.

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Steps to Configure or Establish DLP Policies in Exchange Server

There are 3 ways to define or create Exchange DLP policies using the Exchange Admin Center (EAC). Also use the Exchange Management Shell (EMS) to turn the DLP policies on or off.

  1. Use Policy Templates
    • Microsoft provides default policy templates in Exchange Server that we choose and enforce. Also edit these policies per our organization’s requirements. There are 40 different policy templates. This step is the fastest way to enable DLP in our organization. 
  2. Create Custom Policies
    • Create new DLP policies if we are still looking for predefined Policy Templates that meet our organization’s requirements or needs.
  3. Use Policies from a Vendor

Also get built-in DLP policies from third-party vendors or Microsoft partners and import them into the Exchange Server.

Steps to Choose and Edit Policy Template

See the steps to choose, import, edit, or create Data Loss Prevention policies using the Exchange Admin Center (EAC).

  1. Open Exchange Admin Center and log in as an admin.
  2. Navigate to compliance management > data loss prevention, click the + icon and choose New DLP policy from the template. A new popup browser window opens.

3. Check and select the policy template from the Choose a Template list. Enter the policy name and description if we find one that meets our requirements.

4. Click More Options… and choose the desired option. Before enforcing the DLP policy, we recommend we test it with and without Policy Tips.

5. Click Save.
6. Save policy, select it and click the edit (pencil)
7. Go to rules. Edit the policy rules, such as conditionsactions, and exceptions.
8. Copy, delete, or turn off particular regulations based on the requirements.

Steps to Import Custom DLP Policy

  1. Open Exchange Admin Center (EAC) and navigate to Compliance> data loss prevention.
  2. Click + and choose New DLP Policy from Custom Template.

3. Click More options… to decide whether to immediately enforce or test the policy.
Click Save.
5. After saving, select the policy and click the edit icon to edit or modify the policy rules, conditions, actions, and exceptions per our organization’s requirements.

Steps to Create a New Custom DLP Policy

  1. In EAC, go to ComplianceData Loss Prevention. Then, click + and choose New Custom DLP Policy.
  2. Enter the policy name and description and click Save.

3. Select the custom DLP policy from the list and click the edit (pencil)
4. Click rules.
5. Click + Select sensitive information types to choose the information that needs to be filtered or prevent users from sending or sharing outside the organization.

6. Choose as many conditions as we need and then add action to notify the user or perform any other action.
Add exceptions to prevent false positives.
8. Save the policy.

Exchange DLP Policy Tips

We may also add the Policy Tips for all DLP policies.

Choose one of the 4 options in the Policy Tip:

  1. Notify the sender
    • notification is displayed to the user in the compose window if the DLP detects or policy matches the sensitive information in the collected email. This notification helps users fix the message by removing the info and sending emails without sensitive information.
  2. Allow the sender to override
    • The Policy Tip appears to block the email with an option to override and send the message.
  3. Block the message
    • The message is blocked and not sent. There is no override or any other option available to the user. 
  4. Link to the compliance URL
    • If we choose this Policy Tip, we only have to add a link to our compliance policy for the user to read, understand, and then compose the email.

Once the Exchange DLP policies are defined or created, we test and enforce them when satisfied. Otherwise, we edit and make necessary changes to the policy, try it again, and implement it.

Data Loss Prevention Strategies for Microsoft Exchange Server Conclusion

Data Loss Prevention (DLP) policies are essential to Exchange Server deployment to prevent data leakage and ensure users or employees do not misuse our messaging environment. It also helps in detecting unusual activities. Using the document fingerprinting feature, we enhance the DLP policy to see sensitive or hidden information based on patterns.


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Marion Mendoza

Marion Mendoza

Windows Server and VMware SME. Powershell Guru. Currently working with Fortune 500 companies responsible for participating in 3rd level systems support across the enterprise. Acting as a Windows Server engineer and VMware Specialist.

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