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.
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.
PowerShell supports a command line parameter “WindowStyle” as shown below. The parameter “WindowStyle” sets the window style for that session. Valid values are Normal, Minimized, Maximized, and Hidden.
Most malicious PowerShell scripts run PowerShell with the window style “Hidden”. When the process starts with WindowStyle hidden, no PowerShell console is displayed, so it runs unnoticed for the logged-in user. I created a script to unhide all PowerShell processes. This script can be used during a CERT incident when you want to unhide all PowerShell shells to see what commands are used.
There are ways to log PowerShell commands, but when logs are cleared, unhiding is an option.