Tag Archive: Microsoft 365 Defender

SEC-LABS R&D > Microsoft 365 Defender

Automated attack disruption of Ransomware and BEC – public preview

2023-03-20 0 Comments

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!

Detect, Protect, Respond

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Live response is GA for Linux and macOS

2023-03-01 0 Comments

Live response is designed to enhance investigations by enabling your security operations team to collect forensic data, run scripts, send suspicious entities for analysis, remediate threats, and proactively hunt for emerging threats.

Capabilities

  • Run basic and advanced commands to do investigative work on a device.
  • Download files such as malware samples and outcomes of PowerShell scripts.
  • Download files in the background (new!).
  • Upload a PowerShell script or executable to the library and run it on a device from a tenant level.
  • Take or undo remediation actions.

Requirements

  • macOS – Minimum required version: 101.43.84. Supported for Intel-based and ARM-based macOS devices.
  • Linux – Minimum required version: 101.45.13

Happy Hunting

Respond, Security

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

2023-01-11 0 Comments

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

Detect, Identify, Protect, Security

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Containing unmanaged Devices in Defender

2022-06-20 0 Comments

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.

Detect, Protect, Respond

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Take actions from Threat Hunting in M365 Defender

2022-03-26 0 Comments

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

Detect, Respond, Security

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