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Leadership

Organisational Approach to Technology and Security

How an organization approaches the challenge of technology and security management, well that’s the difference between leveraging technology to deliver value efficiently and effectively vs technical debt and inefficient deployment of technology which may hinder the organisation in its pursuit of its mission.

When we consider how technology is managed, we need to look at it from multiple viewpoints with different views:

Read more “Organisational Approach to Technology and Security” →
Vulnerabilities

Exchange Emergency Mitigation (EM) service

Yesterday I created a honeypot running Exchange 2019 in the lab. I configured very little and setup a test rule as per the MS blog to stop the SSRF from the “Autodiscover” endpoint to the Powershell function call. I put a custom response with some humour (coz why not!) but I disabled the rule:

This rule was placed in the Autodiscover virtual directory which in Exchange by default is here:

C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\autodiscover\web.config

My custom rule:

Read more

<rewrite>

<rules>

<rule name=”RequestBlockingRule1″ enabled=”false” patternSyntax=”Wildcard” stopProcessing=”true”>

<match url=”*” />

<conditions>

<add input=”{REQUEST_URI}” pattern=”.*autodiscover\.json.*\@.*Powershell.*” />

</conditions>

<action type=”CustomResponse” statusCode=”403″ statusReason=”No Hacks for You” statusDescription=”Say no to exploits!” />

</rule>

</rules>

</rewrite>

This morning I checked the Honeypot, and I found the following:

Graphical user interface, text, application, email

Description automatically generated

This rule is hosted in:

C:\inetpub\wwwroot\web.config

<rewrite>

<rules>

<rule name=”EEMS M1.1 PowerShell – inbound” stopProcessing=”true”>

<match url=”.*” />

<conditions>

<add input=”{REQUEST_URI}” pattern=”.*autodiscover\.json.*\@.*Powershell.*” />

</conditions>

<action type=”AbortRequest” />

</rule>

</rules>

</rewrite>

As you can see this was modified at 03:21 01/10/2022

Graphical user interface, text, application

Description automatically generated

This comes from:

Exchange Emergency Mitigation Service (Exchange EM Service) | Microsoft Learn

“Exchange Emergency Mitigation (EM) service”

Text

Description automatically generated

You can check if this is enabled by running the following PowerShell:

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.SnapIn; 

Get-OrganizationConfig | Select-Object MitigationsEnabled

So here we can see that with this enabled, the Exchange server will download and deploy the HTTP re-write rules automatically (if the server has the required version/config etc.)

You can enable or disable it with the following:

Set-OrganizationConfig -MitigationsEnabled $true
Set-OrganizationConfig -MitigationsEnabled $false

You can check this feature works using the following (modify path as required for relevent exchange version)

. "C:\Program Files\Microsoft\Exchange Server\V15\Scripts\Test-MitigationServiceConnectivity.ps1"

Check the MS docs and check your Exchange Server version to see if you have this feature etc.

GCM exsetup |%{$_.Fileversioninfo}

You learn something new everyday!

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