Tag Archive: Defender for Endpoint

New alert suppression configuration

New options with more granular control are available when configuring suppressions

With logical operators like grouping, OR, AND it’s possible to be very granular with the suppressions, which is really critical to avoid suppressing to much.

Always be cautious when adding suppressions

When using the auto-fill rule it will automatically apply all entities from the alert

Resolve or hide an alert

Click Save

Resolving an alert will be handled as a regular resolved alert, meaning ending up in timeline, alerts queue, and APIs

Hiding the alert will cause the alert to be suppressed from the entire system, both on the device’s alerts and from the dashboard and will not be streamed across Defender for Endpoint APIs.

Depending on your scenario it could be important to make the choice to match the scenario you need. Could be related to reporting of total incidents/alerts to customers etc.

Stay safe and 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.

Live response API – build your custom playbooks

PUBLIC PREVIEW FEATURE

We have been able to use Live Response for some time now. It’s really great and we can take the response actions we find necessary and download data from the endpoint through the browser session.

Here is a very high level of how the architecture looks for the live response feature

Some things which may be difficult today with the limitations of single session is we can only connect to one machine at the time and automation does not apply for a browser session

If a machine is compromised in any way it’s useful, but if we want to automate the responses or run the same custom playbook for multiple devices we need to use the API

The API can be used both to collect necessary artefacts from devices, and also take remediation actions.

On some events, we’ve presented how to use the Live Response to dump memory and export the dmp files to Azure storage as an example how powerful it is.

Requirements

Requirements and limitations

  1. Rate limitations for this API are 10 calls per minute (additional requests are responded with HTTP 429).
  2. 25 concurrently running sessions (requests exceeding the throttling limit will receive a “429 – Too many requests” response).
  3. If the machine is not available, the session will be queued for up to 3 days.
  4. RunScript command timeouts after 10 minutes.
  5. Live response commands cannot be queued up and can only be executed one at a time.
  6. If the machine that you are trying to run this API call is in an RBAC device group that does not have an automated remediation level assigned to it, you’ll need to at least enable the minimum Remediation Level for a given Device Group.
  7. Multiple live response commands can be run on a single API call. However, when a live response command fails all the subsequent actions will not be executed.

Minimum Requirements

Before you can initiate a session on a device, make sure you fulfill the following requirements:

Set up service principle with API access

Sample code to connect with the service principle

Connecting to M365Defender

Connect to MDE API ( which applies to this case)

Request

Header

NameTypeDescription
AuthorizationStringBearer<token>. Required.
Content-Typestringapplication/json. Required.

Body

ParameterTypeDescription
CommentStringComment to associate with the action.
CommandsArrayCommands to run. Allowed values are PutFile, RunScript, GetFile.

Available commands

Command TypeParametersDescription
PutFileKey: FileNameValue: <file name>Puts a file from the library to the device. Files are saved in a working folder and are deleted when the device restarts by default.
RunScriptKey: ScriptName
Value: <Script from library>Key: Args
Value: <Script arguments>
Runs a script from the library on a device.The Args parameter is passed to your script.Timeouts after 10 minutes.
GetFileKey: Path
Value: <File path>
Collect file from a device. NOTE: Backslashes in path must be escaped.

Sample Live response request body

Use can upload your own scripts to the library and call the scripts in a similar way as when you use interactive Live Response

POST https://api.securitycenter.microsoft.com/api/machines/1e5bc9d7e413ddd7902c2932e418702b84d0cc07/runliveresponse


{
   "Commands":[
      {
         "type":"RunScript",
         "params":[
            {
               "key":"ScriptName",
               "value":"minidump.ps1"
            },
            {
               "key":"Args",
               "value":"OfficeClickToRun"
            }

         ]
      },
      {
         "type":"GetFile",
         "params":[
            {
               "key":"Path",
               "value":"C:\\windows\\TEMP\\OfficeClickToRun.dmp.zip"
            }
         ]
      }
   ],
   "Comment":"Testing Live Response API"
}

For further reading, please visit

https://docs.microsoft.com/en-us/microsoft-365/security/defender-endpoint/run-live-response

Happy Hunting!