For most Microsoft products, data retention is 30 days. However, it depends on some products if you use the free or paid version of the product, and some products do not allow you to change to the retention period at all. To get a clear overview, I created a table with the most common Microsoft products with their retention period.
Not all products allow you to change the retention period, and some products come with an additional cost when changing the retention period. However, this is not always the case. When a Log Analytics Workspace is attached to Sentinel, data retention if free for 90 days.
Suppose you want to extend the retention period longer than the maximum period. In that case, you need to send the logs to a Security Information and Event Management (SIEM) solution or send it to an Azure Log Analytics workspace if the product supports it.
During an incident, you want to do your analysis as quickly and as precisely as possible. Although there are many scripts available to do proper research within Microsoft 365, if you are working with Exchange Online, OneDrive, SharePoint, they all need separate modules. Not to mention that Exchange Online sometimes need multiple modules depending on what data you want to extract. Using numerous modules can be a pain due to numerous logins that are required.
I wanted to create a ‘One ring to rule them all’ for any incident response within Microsoft 365, which is Operating System independent, runs natively on Windows, and works with or without Multi-Factor Authentication. PowerShell runs on Linux, macOS, natively on Windows, and it happens to be a language I somewhat understand.
Since many Microsoft security products and services connect to the Microsoft Graph Security API, I have chosen to use PowerShell in combination with the Microsoft Graph Security API.
To communicate to the Microsoft Graph Security API, you need an app registration. If you create an app registration, be sure you select the Microsoft graph and Application Permissions.
Note: During the application registration, write down the application ID, the client secret, and the tenant name.
The idea of answering a research question is to run a function, export the outcome to a JSON file, and filter the JSON file if needed. The sign-in logs, for example, contain a lot of information. Using your favorite tool, you can extract what research question you would like to answer. The export includes the location of the login. A simple query makes it possible to filter all logins outside the company’s country to get an overview of potential malicious logins.
The first thing you need to do is getting a token using the app registration you created previously.
Once you have a token, you can use the functions described below.
Note: The token expires in one hour. I have not had this issue myself that a function runs more than an hour, but I am looking to add a refresh token to the script. You can always request a new token described above, which is valid for another hour.
The first thing to look for is licenses. If the tenant contains an Office 365 Advanced Threat Protection license, it helps during the investigation. Or if the tenant contains an Azure AD Premium license, you know the logs in Azure AD go back one month instead of seven days.
I recommend starting with an output of the licenses to see what tools can help during the investigation.
Accepted domains are used in the tenant to sent and receive e-mail. The function RR-GetAcceptedDomains can extract all accepted domains within the tenant.
Getting all accepted domains is helpful to validate which domain names accept e-mail within the tenant.
Many attackers create inbox rules for persistence or hiding footprints. With the function RR-GetInboxRules you can export all inbox rules within the tenant or for a particular user.
The function RR-GetEmailBySubject searches for any e-mail with a given subject.
RR-GetEmailBySubject -subject "thalpius"
The function RR-GetEmailByBody searches for any e-mail with a given keyword in the body of the e-mail.
RR-GetEmailByBody -bodyKeyword "thalpius"
This function gives you the ability to extract all usernames with a given attachment filename in their mailbox.
RR-GetAttachment -fileName "thalpius.zip"
This function gives you the ability to extract attachments to check if it is malicious. It exports all attachments from a user’s mailbox or extracts the attachment itself if you use the attachmentId. The attachment is Base64 encoded. Decode the encoded string in the output to get the binary.
In an illicit consent grant attack, the attacker creates an Azure-registered application that requests access to data such as contact information and e-mail. This function exports all app registrations within the tenant, including the owner.
Every function adds the data to an array. Once you are done running all functions you think you need, RR-OutputArray creates a JSON file with all data. You can filter the data if needed using your favorite scripting language.
According to Microsoft, using Multi-Factor Authentication reduces 99,9% of account compromise attacks within Microsoft 365. Many companies know Multi-Factor Authentication is the right security solution, but what about other security measures?
Here are my top five security measures any company needs to take within Microsoft 365. I even made a downloadable infographic about it.
I want to start by saying that security awareness could easily be number one. I wanted to create a technical top five, but I can not miss out on security awareness as it is essential within any company.
Any given employee needs to be able to identify a threat. Security awareness training helps raise employees’ awareness to identify risks, and the employee then knows what to do when it comes to handling the threat or who to contact.
Security Operations Center
One of the most significant benefits of having a Security Operations Center (SOC) is twenty-four sevenmonitoring. Hackers do not have a nine to five mentality nor work from Monday till Friday. Is there a follow-up on a security threat on a Saturday at ten PM, or do you have to wait for employees to complain on Monday that they can not access their data due to ransomware? Monitoring your environment twenty-four seven is crucial within any company.
SPF, DKIM and DMARC
Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC) are configurations to lower incoming phishing e-mail delivered in the inbox of the user. It is relatively easy to implement and does not come with additional costs. Since a lot of attacks use phishing, implementing SPF, DKIM, and DMARC is a must.
Multi-Factor Authentication and Legacy Authentication
Multi-Factor Authentication and Legacy Authentication go hand in hand since Legacy Authentication does not support Multi-Factor Authentication. So implementing Multi-Factor Authentication is not enough as Legacy Authentication should be disabled as well.
According to Microsoft, more than 99 percent of password spray attacks use legacy authentication protocols, and using Multi-Factor Authentication reduces 99,9% of the attacks within Microsoft Office 365.
In combination with secure awareness, Multi-Factor Authentication and disabling Legacy Authentication is a must within any Microsoft 365 environment.
There are many security measures a company can take. In my opinion, these are the five minimum Microsoft 365 security measures every company needs to take.
There are multiple ways to enable Multi-Factor Authentication (MFA) within Microsoft Office 365. This blog post will describe the various technical implementations of Multi-Factor Authentication, including the best-practice to implement it.
Azure AD MFA Per User
There are three Multi-Factor Authentication statuses within Microsoft Office 365: Enabled, Enforced, and Disabled. The status Enabled indicates that Multi-Factor Authentication is enabled, but the user did not go through the Multi-Factor Authentication registration yet. When the user goes through the Multi-Factor Authentication registration, the status changes to Enforced. Disabled means that Multi-Factor Authentication is not enabled, and the user does not have to log in with a Multi-Factor.
The risk by enabling Multi-Factor Authentication on a user-basis is misconfiguration since Multi-Factor Authentication is not enabled by default when creating a new user account. An administrator can forget enabling Multi-Factor Authentication, which increases the risk of a successful password attack due to missing Multi-Factor Authentication.
Azure AD MFA via Conditional Access
Conditional Access policies at their simplest are if-then statements; if a user wants to access a resource, then they must complete an action. An action can be Multi-Factor Authentication. With Conditional Access, you force every user to use Multi-Factor Authentication when logging into Microsoft Office 365. Using Conditional Access, the risk of misconfiguration lowers since every user applies to the Conditional Access when logging in, and its the best-practice to enable Multi-Factor Authentication.
Note: Azure AD Conditional Access is part of the Azure AD Premium licensing model. So additional costs are required.
Azure AD Named Locations
You can add trusted IP address ranges within Azure AD as Named Locations. A policy can then exclude the Named Locations. Using an exclusion can prevent an identity from being challenged with Multi-Factor Authentication if it comes from a trusted location.
Azure AD Identity Protection MFA Registration Policy
The advantage of using the Multi-Factor Authentication policy within Azure AD Identity Protection is that users have 14 days to complete the registration. During these 14 days, they can bypass registration, but they have to register before they can complete the sign-in process at the end of the period. Once the sign-in process is complete, the user can log in without Multi-Factor Authentication. The policy only forces a user to register Multi-Factor Authentication. The Azure AD Identity protection policy is unnecessary when Multi-Factor Authentication is enforced using Conditional Access.
Note: Azure AD Identity Protection is part of the Azure AD Premium licensing model. So additional costs are required.
Enabling this option configures your organization with the following settings:
Requiring all users to register for Azure Multi-Factor Authentication;
Requiring administrators to perform multi-factor authentication;
Blocking legacy authentication protocols;
Requiring users to perform multi-factor authentication when necessary;
Protecting privileged activities like access to the Azure portal.
Note: Azure AD Security Defaults are not suitable for complex security requirements. It is either turned on or turned off. If you want to make decisions based on a condition, Conditional Access is the way to go.
Microsoft Azure Active Directory supports several authentication and authorization protocols, including legacy authentication. Legacy authentication includes Exchange ActiveSync, SMTP, Autodiscover, Exchange Web Services, POP3, IMAP4, and many more.
The problem is, legacy authentication does not support Multi-Factor Authentication!
According to Microsoft, more than 99 percent of password spray attacks use legacy authentication protocols. It is crucial to disable legacy authentication when using Multi-Factor Authentication or in any situation.
You can use the Azure portal to identify the usage of legacy authentication within your environment before disabling it.
Navigate to; Azure portal > Azure Active Directory > Sign-ins.
Add the Client App column if it is not shown by clicking on; Columns > Client App.
Add filters > Client App > select all of the legacy authentication protocols. Select outside the filtering dialog box to apply your selections and close the dialog box.
Note: Conditional Access in Report-only mode is another way to identify legacy authentication within your environment.
According to Microsoft, using Multi-Factor Authentication reduces 99,9% of the attacks within Microsoft Office 365. Using Multi-Factor Authentication does not mean your company is safe for password attacks. It would not be the first time a user accepts a Multi-Factor Authentication challenge on their device when an attacker logs-in within Microsoft Office 365 with leaked credentials. So adoption and education for company users are critical. Enabling Multi-Factor Authentication and disabling legacy authentication is a minimum security measure every organization should take.
A Computer Emergency Response Team (CERT) is a group of information security experts responsible for responding to an organization’s cybersecurity incident. When an event occurs within Office 365, many products can help identify and mitigate the threat, including Microsoft Office 365 Advanced Threat Protection (ATP). Microsoft Office 365 ATP is part of Office 365 E5, Microsoft 365 E5, or Microsoft Security E5. Other tools within the Microsoft 365 E5 suite can help you identifying and mitigating an incident, but what if you do not have an E5 license? In this blog post, I will go more in-depth about what to do if you do not have Microsoft Office 365 ATP with just the portal on a single identity.
The first thing I would recommend to do during an incident within Office 365 is to check if a mailbox needs a Litigation Hold. Litigation Hold can preserve all mailbox content, including deleted items and original versions of modified items. The second thing I would recommend is to check what license plans are available within the tenant. Looking at the license plans helps identify which tools are available within the tenant. The last thing I would recommend is to be in control as quickly as possible. If you identified a compromised user, initiate a password reset as soon as possible to prevent lateral movement. Do not forget to sign-out this all Office 365 sessions.
To initiate a sign-out from all Office 365 sessions, go to Users > Active users from within the Office 365 portal, click on the user account to open the user’s properties page, and click initiate sign-out.
Unfortunately, this does not mean you are in control of the situation. One of my biggest concerns is: What did the attacker find in the mailbox? Did the attacker recover a password that the attacker can use to login to another inbox and get undetected? Did the attacker recover a password for a third-party application outside the tenant, but which can have a business impact?
If there is any indication that an attacker was logged-in to a mailbox, you can search for malicious activities. There is an option to export all search history, which can help identify what the attacker was looking for in the inbox. Exporting the search history can be done by going to Settings in the top right corner within Office 365, click on View all Outlook settings, go to General, go to Privacy and data.
Most hackers use persistence to keep a connection to the inbox. Persistence can be as simple as mail forwarding rules, inbox rules, or a combination of the two.
To get the forwarding rules and inbox rules, go to Settings in the top right corner within Office 365, click on View all Outlook settings, go to Mail, followed by Forwarding and Rules.
Most hackers want to be undetected as long as possible. A way to be undetected is to delete all incoming e-mails using a rule and remove them from the deleted items. Luckily, the recovery of these items is possible: Open the user’s inbox, go to Deleted Items, and click Recover items deleted from this folder.
Illicit consent grant attack is an attack where a malicious user creates an Azure-registered application that requests access to data such as contact information, e-mail, or documents. The malicious user needs to trick a victim into going to a website and grant access to their account.
To check if a user granted application consent to access their data., go to Azure Active Directory, Users, Select the user, and click Applications. Be sure the list does not contain malicious applications.
Sign-ins and Audit logs
The sign-ins and audit logs from the Azure Active Directory give you a lot of information about the identity. The Sign-ins and audit logs include the location of sign-in, IP address, client application used, user agent, device info, identity activities, etc.
To get the Sign-ins and Audit logs, go to Azure Active Directory, Users, Select the user, and click Sign-ins or Audit logs.
Use the Content search and Audit log search to find all tenant activities, including file activity, folder activity, SharePoint list activity, Exchange mailbox activity, etc. You can use the content search tool to search for e-mail, documents, and instant messaging conversations based on conditions like date, sender, recipients, subject, etc.
Note: Audit log search is not turned on by default. Microsoft is changing the default option, so it is enabled by default soon. If the option is disabled, you will see a message saying Turn on auditing.
With eDiscovery, you can do the same as with Content search, but now you are creating a case that you can use to handle the incident. You can add engineers to the case, set mailboxes and data on hold that are part of the case, etc. Advanced eDiscovery is the same as eDiscovery, except you get many more settings and options.
To track the flow of e-mail messages in your organization, you use Message Trace. If you want to know which e-mail sent to whom in what time range, Message Trace is the tool within the portal.
The last view I can recommend is the Alert View. The alert view gives a good overview of any risk level alerts available within the tenant.
With just the portal and no E5 licenses, it is “hard” to investigate an incident. In another blog post, I will go in-depth to do a proper analysis with tooling like PowerShell.