Detect

Automated attack disruption of Ransomware and BEC – public preview

Automated attack disruption of Ransomware and BEC (Business email compromise uses high-confidence Extended Detection and Response (XDR) signals across all workloads; endpoints, identities, email, and SaaS apps, to contain the threat quickly and effectively, to stop further impact.

These 2 scenarios are common attacks and it’s really great that they are supported by the feature in Microsoft 365 Defender.

Business Email Compromise, BEC

Threat actors are impersonating executives to trick, for example, Economic department to transfer money by impersonating the CFO or the CEO.

Automatic attack disruption can help to detect these attacks and remove the access to the accounts by disabling the compromised account, limiting their ability to send fraudulent email

Human-operated ransomware, HumOR

This attack, commonly used today, is devastating for an organization. The threat actors has full control of the environment and have usually controlled the environment for some time.

The challenge from a SecOps perspective is to be fast enough to respond to the incidents and mitigate accounts and the devices fast enough.

When the threat actors has gained privileged access, things move very quick and automatic attack disruption will contain the spreader device and disable the compromised user account

Automatic attack disruption operates in 3 key stages

  • Detect malicious activity and establish high confidence
  • Classification of scenarios and identification of assets controlled by the attacker
  • Trigger automatic response actions using the Microsoft 365 Defender protection stack to contain the active attack

First the detection will happen, which is achieved by AI, research-information etc.., to establish a high level of confidence in accurately detecting ransomware spread and encryption activity. The XDR-level capability correlates insights across endpoints, identities, email and SaaS apps to establish high-fidelity alerts.

A second stage will aggregate automatic analyze the activities like tampering, backup deletion, credential theft, mass lateral movement and many more to flag the assets included in the chain and trace the activities back to the remote execution TTP

Distrupting the attack

Response actions against the entities which are identified as compromised and in the public preview these two are the main actions:

When this happens, it will be visible in the:

Incident queue

  • A tag titled “Attack Disruption” next to affected incidents

If you really must exclude some user from the automatic attack disruption, then you can do it in the MDI settings

Incident page

  • A tag titled “Attack Disruption”.
  • A yellow banner at the top of the page that highlights the automatic action taken.
  • The current asset status is shown in the incident graph if an action is done on an asset, e.g., account disabled or device contained.

Some thoughts

It’s important that prerequisites are fixed, like MDI Action Account (if not using built-in system account) and

For further reading, please visit
Automatic attack disruption in Microsoft 365 Defender | Microsoft Learn

Stay safe, Protect the world and Happy Hunting!

Near Real Time Rules in Defender

If you want to find threats earlier it is now possible to use NRT rules in Defender.

Before this, we had the options to use 24h, 12h, 3h, and 1h as the schedule. This gives Defenders the possibility to detect and respond to threat much earlier.


Tables that support Continuous (NRT) frequency

  • AlertEvidence
  • DeviceEvents
  • DeviceFileCertificateInfo
  • DeviceFileEvents
  • DeviceImageLoadEvents
  • DeviceLogonEvents
  • DeviceNetworkEvents
  • DeviceNetworkInfo
  • DeviceInfo
  • DeviceProcessEvents
  • DeviceRegistryEvents
  • EmailAttachmentInfo
  • EmailEvents
  • EmailPostDeliveryEvents
  • EmailUrlInfo
  • UrlClickEvents

The NRT rules does not support externaldata operator and you can only query one table

Configuring NRT (Continuous) Rule

From the Advanced Hunting, develop your query and click and configure the Alert Details

Click Next and select impacted entities (in this case we are using an email table and therefore the impacted entities will be mailbox)
Click Next and configure the actions.
It’s important to think about what the actions means and make sure your query will detect exactly what you want.

Be cautious with the Isolate device when querying Device tables. If you have an error in your detection you may isolate all machines by mistake

It’s now completed!

Don’t forget that you can use the hunting if you want to take response actions on multiple entities very quickly.

From the Result of your hunting query, select the rows where you want to take action and click Take Actions

This brings your the Actions pane and you can choose which actions you need.

Depending on your query (which tables and output) you get different options for your actions. ‘

Stay safe, and Happy Hunting!

Tamper Protection for Exclusions in Defender

One thing that threat actors commonly do when getting a foothold on a device, is to try to disable Defender services and adding exclusions for their tools which they plan to execute.

For the Defender services, we have had Tamper Protection for some time, but that did not cover exclusions.

Tamper Protection configuration via Intune

Requirements

For Tamper Protection to cover exclusions, the following requirements must be met:

Disable Local Admin Merge

Verifying and troubleshooting

The registry value TPExclusions which is in the HKLM\SOFTWARE\Microsoft\Windows Defender\Features key shows a value of 1 if protected and 0 if not protected. Please note that you cannot change the registry value to protect the exclusions, it’s for information and not configuration

While we talk about Antivirus policies…

We would like to share this as well since it’s something we see when we do Defender assessments, it’s unfortunately very common that these settings are wrong

Cloud block level (high is recommended minimum) and Cloud Extended Timeout check must be set to 50 (seconds)
Sample submission is required for Cloud protection

And for

Happy Hunting!

Taking actions on on-prem accounts with MDI Action Account, troubleshooting

Background

The response action of blocking a compromised account is important to have available. Regardless of solution one must be able to quick and easy be able to block an account.  In MDI (part of Microsoft 365 Defender) it is possible since some time ago to configure an MDI Action Account, lately the option to run with the system account of the Domain Controller has been added to this feature and therefor you don’t have to configure the gMSA account.

Using system or a custom gMSA account

The choice is made based on organizational structure, Tiering/RBAC, MSSP partner. Basically, if you are required to delegate the permissions to only allow actions on accounts in certain OU’s, then you must use a custom gMSA accounts.

For example, if you have a MSSP partner monitoring your security and take actions to discovered threats, a so called MDR (Managed Detection and Response), you have an option to control to which accounts the MSSP can take actions.

The available actions are:

  • Disable user in Active Directory: This will temporarily prevent a user from logging in to the on-premises network. This can help prevent compromised users from moving laterally and attempting to exfiltrate data or further compromise the network.
  • Suspend user in Azure Active Directory: This will temporarily prevent a user from logging in to Azure Active Directory. This can help prevent compromised users from attempting to exfiltrate data and minimizes the time between Disable user in Active Directory and the sync of this status to the cloud.
  • Reset user password – This will prompt the user to change their password on the next logon, ensuring that this account can’t be used for further impersonation attempts.

From an MSSP perspective, this feature is very useful since there wouldn’t require customer access (VPN or other kind of access) to respond to threats. Even though this feature is very popular for MSSPs, you will still want to have this option if you have your internal security operations to be able to respond from the portal you are currently working in.

Even though this feature is very popular for MSSPs

To learn how to create and configure the gMSA account you can start with this link
https://learn.microsoft.com/en-us/defender-for-identity/manage-action-accounts

Troubleshooting

(The troubleshooting path will be updated based on troubleshooting session done with customers)

There 2 primary sources for troubleshooting this, sensor logs and event logs. Preferably the logs are sent to SIEM solution (like Microsoft Sentinel).

Using Sentinel (or look in the event viewer, or if you have another SIEM solution in place).

SecurityEvent | where Account has "gMSA-MDIAction$"

Note the $ character in the account name, gMSA account is more like a computer account. It’s the type of msDS-GroupManagedServiceAccount.

If the account doesn’t have logons ending with a $ (like a computer account), then it’s not a gMSA account and start there by creating a one.

https://learn.microsoft.com/en-us/defender-for-identity/manage-action-accounts

This can also be checked on the logon event (this will trigger 4625, logon failed)

Verify that the AccountType is “Machine”

Successful sign-in:

Account is not allowed to logon as a service

If the gMSA Account is setup and configured correctly and there is still event 4625 being logged.

Check the Status property of the login event

0xc000015b indicates that the account is not allowed to login0xC000015B

STATUS_LOGON_TYPE_NOT_GRANTED, A user has requested a type of logon (for example, interactive or network) that has not been granted. An administrator has control over who can logon interactively and through the network.

More information about the Status property can be found here:

https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4625

https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/596a1078-e883-4972-9bbc-49e60bebca55

To address this issue you need to create a new or update existing policy to allow that account to logon as service on the target system (the DCs)

https://learn.microsoft.com/en-us/system-center/scsm/enable-service-log-on-sm?view=sc-sm-2022#enable-service-log-on-through-a-local-group-policy

Successful events effecting the user you try to take action on

The following query will find events of enabling and disabling a user

SecurityEvent
| where EventID in(4738,4725,4722)
| where Account contains "gMSA-mdi-action$"
| where TargetAccount contains "test" //the user you want to take action on
You see 4738 “A user account was changed” at the same timestamp as the 4725 and 4722 and the 4738 event show the UAC 0x10: Account Enabled and 0x11: Account Disabled

https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4738

Hope this helps!

We will continue to update this post if we run into other related troubleshootings

//Happy Hunting

Containing unmanaged Devices in Defender

For a long time we have been able to isolate onboarded devices in Microsoft Defender for Endpoint. But if a device is not onboarded we could not take any response actions to an eventual threat.

Microsoft has released a feature called Contain device which basically makes the opposite, instead of isolating the compromised device, we can tell all managed devices that they cannot communicate with the specific unmanaged device.

If a contained device changes IP address, the blocking will be updated and changed to the new IP address and the old will be “released” from block.

Defender troubleshooting mode

Troubleshooting mode will make it possible for local admins on the endpoint to override Antivirus policy on the device, including tamper protection. When enabled it give the admin a 3 hour window to do what was intended. After the 3 hour window, the settings will be re-applied again.

Enabling Troubleshooting mode

Go to the Device page in Microsoft 365 Defender and click on the 3 dots menu item and select troubleshooting mode

In the Device action center we can see the following entry

Prerequisites

  • Windows 10 (version 19044.1618 and above)
    Windows 11
    Windows Server 2019
    Windows Server 2022
  • Microsoft Defender for Endpoint must be tenant-enrolled and active on the device. 
  • The device must be actively running Microsoft Defender Antivirus, version 4.18.2203 and above. 

Hunting for events

//Use the following ActionType and the DeviceEvents table
DeviceEvents
| where ActionType == "AntivirusTroubleshootModeEvent"  

Happy Hunting!

Defender Firewall report in Microsoft 365 Defender

One challenge with configuring Windows firewall (besides default of block inbound and allow outbound) is that we need the data. Before Defender for Endpoint we had to rely on event forward and similar techniques to get the data of the environment.

Microsoft has recently released a Defender Firewall (Windows Firewall) report where we can see the events. This has some prerequisites in terms of audit settings (Windows audit settings, not the firewall log)

Configure firewall auditing

Enable auditing for Filtering platform

Always verify eventual impact in your environment before enabling new settings on all endpoints

To get the data, it requires the device to be onboarded to MDE

Command line to enable auditing

  • auditpol /set /subcategory:”Filtering Platform Packet Drop” /failure:enable
  • auditpol /set /subcategory:”Filtering Platform Connection” /failure:enable

For further reading about filtering platform auditing, please visit:
Audit Filtering Platform Connection (Windows 10) | Microsoft Learn
Audit Filtering Platform Packet Drop (Windows 10) | Microsoft Learn

When the settings are completed, you will see data populate at

https://security.microsoft.com/firewall

You will be able to see inbound, outbound and apps in the report on a very detailed level which will make it easier to harden the policy.

Hunting for Firewall events

The firewall events are located in the DeviceEvents table
DeviceEvents
| where ActionType startswith "Firewall"

Happy Hunting

Switching tenant in Microsoft 365 Defender

[Updated post]

What’s described in this post is no longer applicable due to TID parameter are added to links in the portal

We developed an extension that does exactly the same thing but this is not needed anymore hence why we won’t release it. Microsoft has updated links in the portal to include the TID-parameter which is awesome and for people working with many customers this is really great news and you don’t need multiple profiles either!

[Old post]

If you work with multiple customers with Microsoft 365 Defender or working in a multi-tenant setup, you have probably noticed that your end up in the first tenant even if changing the tid-parameter in the url.

The reason why this happens is that when for instance, clicking on links in Defender, it will take you to the tenant stored in a cookie, especially if you don’t have the tenant id parameter in the link.

It can be addressed by working with multiple profiles, but if you don’t want that you can just do the following

Open dev tools and go to Application and expand Cookies
Select the security.microsoft.com and right-click on sccauth and select delete

Refresh the page

Happy Hunting!

Tuning insights in Microsoft Sentinel

Fine-tuning the analytic rules to minimizing the number of false-positives can be time-consuming and you still want to keep the high visibility so you don’t want to risk false-negatives. At the same time, the risk of managing a high number of incidents, especially if they are false-positives, would also be time-consuming.

To be able to fine-tune the analytic rules, we need historical data. Same as what was needed when developing the detection in the first place and for fine-tuning we also need decisions made when classifying the incident and if those decisions was related to any specific entities.

Machine Learning to the help

Microsoft Sentinel uses machine learning to analyze signals from the data sources and the responses made to an incident over time to assist and providing data for fine-tuning decisions.

The rules with recommendations for a fine-tune is noted with a light bulb next to the rule name as in below picture.

fine-tuning recommendations
Fine-tuning recommendations available (preview feature)

When editing the analytic rule, in the Rule Logic tab, the Tuning insights is available

There are several panes which can be scrolled through which contains actionable items like exclude accounts, IPs etc. from the analytic rule

The third pane shows the importance of correct mapped entities since this is the only way to get results and shows the four most frequent entities in the alerts generated by the analytic rule.

Hopefully this can share some light on make your work more effective by working with your analytic rules to make your detection better.

Don’t forget to be careful and thing through your exclusions to avoid losing visibility.

For further reading, please visit

https://docs.microsoft.com/en-us/azure/sentinel/detection-tuning

Happy Hunting!

Sec-Labs Team

Take actions from Threat Hunting in M365 Defender

We wrote a blog post earlier about the news in threat hunting

New features in Advanced Hunting – Microsoft 365 Defender – SEC-LABS R&D

Another feature in hunting, which will speed up responses from a threat hunting scenario is Take Action

When selecting a record in the result, the Take Action button will be visible as seen in below picture

take actions, m365 defender

So instead of just creating a new incident or adding events to an existing incident we can take actions from the hunting experience.

In the Take actions experience we have actions grouped by Devices, Files and Users.

actionable items, m365 defender

The action options available is dependent on the data in the result. For instance, file information like checksum is required to being able to quarantine a file.

When clicking Next we can see the target selected and click Next

We can add a Remediation name and Description for our action

This feature enables a rapid response at the fingertips of the threat hunters for immediate actions

For further information, please visit

https://docs.microsoft.com/en-us/microsoft-365/security/defender/advanced-hunting-take-action?view=o365-worldwide

Happy Hunting!

Sec-Labs Team