Microsoft Teams: Protect against Phishing & Malware

Pretend for a moment that I am a marketing agency you just hired, and invite me as a guest to a team in Microsoft Teams to collaborate. What happens if that guest’s account gets compromised and a bad actor gains access to your team in Microsoft Teams? Your organization is having sensitive conversations there, uploading sensitive files, and if that data were to be publicly disclosed, could do damage to the organization. More importantly, a bad actor can post hyperlinks to “phishing” web sites, and upload malicious files into Microsoft Teams – from there users can open the links or run the files, posing a serious threat to your organization’s security.

How do we help to protect against phishing attacks and malicious files in Microsoft Teams? Office 365 Advanced Threat Protection is here to help. In fact, Office 365 ATP can also help to protect against phishing and malware in not just Microsoft Teams, but Exchange Online, SharePoint, and OneDrive! More information in the Service Description here.

To configure, once the appropriate licenses have been purchased and assigned to each user, open the Office 365 Security & Compliance Center (protection.office.com) -> Threat Management -> Policy and click on ATP Safe Attachments:

Check the box Turn on ATP for SharePoint, OneDrive and Microsoft Teams and click Save:

 


Now, when a malicious file is uploaded to Microsoft Teams, Office 365 ATP will perform a detonation of the file (following this process). Here we have files in Microsoft Teams, are they malicious?

If the file is indeed malicious, when the user attempts to execute the file in Microsoft Teams, they will receive the following message:

Safe Attachments stops the user in their tracks, and never gives them the opportunity to launch the file. This same behavior also occurs when the file is executed directly from SharePoint. If using Office 365 Alerts (in the Security & Compliance center), and alert can be configured to notify the admin that malware was uploaded to Microsoft Teams:

Here’s what the alert looks like:

(Note, if using Microsoft Cloud App Security an SMS notification can be sent, and MCAS also offers integration into your SIEM.)

What about phishing links in Microsoft Teams? If the ATP Safe Links policy is correctly configured (more information here), then when a phishing hyperlink is posted, the user will receive a blocking message when attempting to click on the hyperlink. Let’s take a loot at this below, here’s a hyperlink in a team conversation in Microsoft Teams:

When the user clicks on the link, ATP Safe Links and the Intelligent Security Graph goes into action to provide protection. ATP recognized the website is malicious, and stops the user in their tracks, not giving them the opportunity to click through to the original website. (Although, that can be changed in the policy).

Conclusion:

Office 365 Advanced Threat Protection provides protection against advanced thread such as phishing and malware for not only your email in Office 365, but also Microsoft Teams! What if everyone had this enabled? The world might just be a safer place! Enjoy!

Block OneDrive Downloads and Audit OneDrive Activity! (SharePoint too!)

Do you have a business requirement to block the download of specific files or file types from OneDrive? What about detailed auditing to understand what files are downloaded or viewed? Well, today is your lucky day – because this is all possible with Microsoft security technology and takes minutes to create. I’m going to walk you through how to do this, and in return, make you look like an IT Rockstar to your organization!

Note: There are other methods to restrict those files from being synchronized using the OneDrive desktop client, we won’t cover those today however (but are accessible in the SharePoint Online Admin Portal)

IMPORTANT: Nothing is 100% secure and it’s all about defense in depth. If you want that extra ply in the tinfoil hat, I highly recommend protecting and encrypting those files with Azure Information Protection as that extra layer of protection.

Also, it’s important to note,the method below at the time of this writing is in public preview.

Background:

My organization, an engineering firm, designs buildings for their commercial and government clients. These design plans often contain additional documentation that are in the form of a .PDF and sometimes photos in the form of a .JPEG (or .jpg).

Scenario:

These .PDF and .JPEG files are highly confidential and thus we want to make sure they never leave OneDrive in Office 365 and can only be viewed in a web browser. In other words, we need to block the ability for an end-user to download these two file types from OneDrive. So, how do we do this?

Solution:

Azure Active Directory Conditional Access and Microsoft Cloud App Security Conditional Access App Control to the rescue! These two products are part of Microsoft 365 E5 or EMS E5 or my new favorite: Microsoft 365 E3 + Identity & Threat Protection. The two products that make up this solution are Azure Active Directory and Microsoft Cloud App Security.

Let’s take a look at how to do this!

Step 1: Create a Azure AD Conditional Access Policy

From within the Azure portal -> Azure Active Directory -> Conditional Access -> New Policy I am going to create a new policy. First, give it a name, “OneDrive Block JPEG and PDF”. Next, assign it to specific users or groups of users. For testing purposes I’m assigning to Adele Vance (IMPORANT: Don’t lock yourself out! Careful planning is required when assigning to all users).

 

 

Next, add Office 365 SharePoint Online as the application to be applied to:

 

 

Under Session, select Use Conditional Access App Control, then click Done.

Next, click Enable policy to enable the policy and click Create.

 

Step 2: Launch OneDrive (via portal.office.com)

Wait 15 minutes for the new Conditional Access policy to propagate. Next, open a new browsing session (inprivate or on another computer) and logon as the test user that was just assigned to. In my case, I am going to sign in to portal.office.com in an in-private session as Adele. Browse to OneDrive in the Office portal and open a file in the web browser. Sign out of this web browsing session when done.

Step 3: Configure Microsoft Cloud App Security

We now need to configure Microsoft Cloud App Security (CAS) and create the appropriate policies.

To start, validate that OneDrive is a connected application by browsing to http://portal.cloudappsecurity.com and navigating to Investigate -> Connected Apps. Notice OneDrive for Business will be listed and connected: (Yes, you can also connect CAS to G-Suite, Box, and other apps!)

 

Next, click on Conditional Access App Control apps and OneDrive for Business will also be displayed:

Step 4: Create the Session Policy in Microsoft Cloud App Security

Next, we need to create the policy that will provide the session control when Adele uses OneDrive in the Office 365 Portal. To do this navigate to Control -> Policies, click New Policy and select Session Policy.

 


 

Let’s give the policy a name and description:

 

Next, under Session control type select Control file download (with DLP). Under Activity source and activity filters configure configure them per the screenshot below

 

 

Scroll down (leave content inspection blank and don’t check the box) and under Actions select Block. OPTIONAL: Configure user email notification or customize block message. When finished at the bottom of the page click Create.

Step 5: Test the User Experience

Now it’s time to test and validate this is the behavior we want. Open a new web browsing session and login as the test user. In my case, I’m going to login to portal.office365.com using Adele Vance’s account in an in-private browser session.


 

Once signed in, navigate to OneDrive in the Office 365 Portal. When you click on OneDrive, notice the splash page indicating this site is being monitored!

 

 

 

 

Also, notice the address of the site. It’s being proxied through CAS.MS indicating this session is being controlled by Cloud App Security:

 

Click Continue to Microsoft OneDrive for Business

Notice I have two files, a .PDF and a .JPEG in the OneDrive folder:

 

Hover the cursor over the PDF and click the ellipses, and select Download

 

Notice, the file download is blocked with a splash message indicating it’s blocked!

 

Now, I know what you’re wondering, “Matt what’s that file it wants to save?” When I open that file, it’s just a warning:

 

From here, within the Cloud App Security Portal, I can audit the activity and receive additional details around this attempt:

Additional alerting can be generated, with an email or SMS notification sent. Imagine having CAS send an email to your ticket system so you can be notified of this violation? What about sending to your SIEM? Endless possibilities.

Conclusion:

As you can see, with a bit of an open mind and creativity, possibilities to build true security solutions that lead to a real business outcome, is entirely possible. The total time spent creating this solution was 10 minutes. Don’t forget to test (which obviously will add to the 10 minutes) all the scenarios for this. Questions? Let me know in the comments below!

Enjoy and help us make this world more secure! –Matt Soseman

Microsoft Teams: Protecting against advanced threats

How well do you trust your employees? What about your vendors? I’m constantly coming across organizations that are storing intellectual property and other sensitive data in Microsoft Teams, so they can collaborate with that data in a centralized manner. I’m also learning that most of those organizations are enabling guest access, and allowing outside vendors to have access to that data and the resources within the team. A good example of this is an outside marketing agency that you contract with for event marketing, online marketing, etc. What if a guest of that team (or employee), accidently (or intentionally) uploads malware to the team (but masks it as a file called MarketingRoadmap.pptx), and an employee of the organization opens the file? The malware could now spread throughout your environment.

This is where Office 365 Advanced Threat Protection (ATP) comes in. ATP can help to safeguard your organization from this threat by “detonating” (executing) files uploaded to Microsoft Teams (specifically the SharePoint/Office 365 Group on the back-end) to validate it is a legitimate file and contains no malicious code that can do harm. This feature comes with Microsoft 365 E5, Office 365 E5, or available as an add-on to an existing Office 365 subscription.

Too Long Don’t Read (TLDR):In this blog, I’m going to describe how to enable this feature, perform a test, and show you alerting. For details on how Office 365 Advanced Threat Protection for SharePoint, Microsoft Teams, OneDrive works and it’s architecture, see the below diagram – and read the following article: Office 365 ATP for SharePoint, OneDrive, and Microsoft Teams

Office 365 Advanced Threat Protection Architecture:

How to enable Office 365 Advanced Threat Protection:

Note: I will not be discussing Office 365 ATP for Exchange Online.

To enable, simply browse to the Office 365 Security & Compliance Center (protection.office.com) -> Threat Management -> Policy and click ATP Safe Attachments:

Once in ATP Safe Attachments, check the box Turn on ATP for SharePoint, OneDrive and Microsoft Teams and click Save:

IMPORTANT: Review the Safe Attachment policies and configure as appropriate. Consider running Set-SPOTenant to DisallowInfectedFileDownload in PowerShell for the SharePoint tenant
to ensure the malicious files cannot be downloaded. For more information see Turn on Office 365 ATP for SharePoint, OneDrive, and Microsoft Teams

User Experience:

If a malicious file is uploaded, and detected by ATP, the user will be unable to open the file. If the user browses to the Office 365 Group or SharePoint site where the file is stored, and attempts to run from there, they will be presented with the following:

Setting up an alert:

As the admin, I want to be notified when this activity occurs. Using Office 365 Alerts I will create an Alert Policy to notify me so I can take action:


When the alert notification arrives via email, here is an example of what it looks like:

Clicking Investigate will launch the alert in Office 365 Alerts (notice I can suppress, or notify users):

Accessing the event via Threat Explorer gives me access to additional details and advanced analysis that could be helpful in my investigation of the threat:

Conclusion

Office 365 Advanced Threat Protection is one of the many layers in your defense in depth approach to cyber security, and with it’s ease of administration and use, it can be a valuable tool to protect your organization. Enjoy! –Matt Soseman