Tuesday, April 13, 2021

Apply Microsoft April 2021 Security Update to Mitigate Newly Disclosed Microsoft Exchange Vulnerabilities


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Apply Microsoft April 2021 Security Update to Mitigate Newly Disclosed Microsoft Exchange Vulnerabilities

Original release date: April 13, 2021

Microsoft's April 2021 Security Update mitigates significant vulnerabilities affecting on-premises Exchange Server 2016 and 2019. An attacker could exploit these vulnerabilities to gain access and   maintain persistence on the target host. CISA strongly urges organizations to apply Microsoft's April 2021 Security Update to mitigate against these newly disclosed vulnerabilities. Note: the Microsoft security updates released in March 2021 do not remediate against these vulnerabilities.

In response to these the newly disclosed vulnerabilities, CISA has issued Supplemental Direction Version 2 to Emergency Directive (ED) 21-02: Mitigate Microsoft Exchange On-Premises Product Vulnerabilities. ED 20-02 Supplemental Direction V2 requires federal departments and agencies to apply Microsoft's April 2021 Security Update to mitigate against these significant vulnerabilities affecting on-premises Exchange Server 2016 and 2019.

Although CISA Emergency Directives only apply to Federal Civilian Executive Branch agencies, CISA strongly encourages state and local governments, critical infrastructure entities, and other private sector organizations to review ED 21-02 Supplemental Direction V2 and apply the security updates immediately. Review the following resources for additional information:

Microsoft April 2021 Security Update Summary

New DNS Vulnerabilities, Impacting 100+ Millions of Enterprise and Consumer Devices

 Forescout Research Labs, partnering with JSOF Research, disclose NAME:WRECK, a set of nine vulnerabilities affecting four popular TCP/IP stacks (FreeBSD, Nucleus NET, IPnet and NetX). These vulnerabilities relate to Domain Name System (DNS) implementations, causing either Denial of Service (DoS) or Remote Code Execution (RCE), allowing attackers to take target devices offline or to take control over them.

The widespread use of these stacks and often external exposure of vulnerable DNS clients lead to a dramatically increased attack surface. This research is further indication that the community should fix DNS problems that we believe are more widespread than what we currently know.

This research uncovered vulnerabilities on very popular stacks:

1. Nucleus NET is part of the Nucleus RTOS. The Nucleus RTOS website mentions that more than 3 billion devices use this real-time operating system, such as ultrasound machines, storage systems, critical systems for avionics and others. The most common device types running Nucleus RTOS include building automation, operational technology and VoIP.

2. FreeBSD is widely known to be used for high-performance servers in millions of IT networks and is also the basis for other well-known open-source projects, such as firewalls and several commercial network appliances. The most common device types on Device Cloud running FreeBSD include computers, printers and networking equipment.

3. NetX is usually run by the ThreadX RTOS. Typical applications include medical devices, systems-on-a-chip and several printer models. ThreadX was known to have 6.2 billion deployments in 2017, with mobile phones (probably in baseband processors), consumer electronics and business automation being the most common product categories. The most common device types running ThreadX include printers, smart clocks and energy and power equipment in Industrial Control Systems.

Organizations in the Healthcare and Government sectors are in the top three most affected for all three stacks. If we conservatively assume that 1% of the more than 10 billion deployments discussed above are vulnerable, we can estimate that at least 100 million devices are impacted by NAME:WRECK.

The details of these vulnerabilities are described in our technical report and will be presented at Black Hat Asia 2021.

Helping the community to fix DNS vulnerabilities

Disclosing these vulnerabilities to vendors provides much-needed information and education on the impacted products and continues the dialogue in the research community:

1. We urge developers of TCP/IP stacks that have yet to be analyzed to take the anti-patterns available in our technical report, check their code for the presence of bugs and fix them. To help with this process, we are releasing open-source code developed for the Joern static analysis tool. This code formalizes the anti-patterns we identified, allowing researchers and developers to automatically analyze other stacks for similar vulnerabilities.

2. We invite researchers, developers and vendors to reach out to us if they are interested in a set of small proof-of-concept crashing network packets for the identified anti-patterns. These packets can be used to automatically test intrusion detection rules.

3. We realized that many vulnerabilities exist because RFC documents are either unclear, ambiguous or too complex. To help prevent such issues from reappearing in the future, we have submitted to the IETF an informational RFC draft where we list the anti-patterns we identified and how to avoid them while implementing a DNS client or server.

Recommended Mitigation

Complete protection against NAME:WRECK requires patching devices running the vulnerable versions of the IP stacks. FreeBSD, Nucleus NET and NetX have been recently patched, and device vendors using this software should provide their own updates to customers.

However, patching devices is not always possible, and the required effort changes drastically depending upon whether the device is a standard IT server or an IoT device.

Given the challenges of patching, we also recommend the following mitigation strategy:

1. Discover and inventory devices running the vulnerable stacks. Forescout Research Labs has released an open-source script that uses active fingerprinting to detect devices running the affected stacks. The script is updated constantly with new signatures to follow the latest development of our research. Forescout customers using eyeSight can also automatically identify devices using FreeBSD, Nucleus RTOS, ThreadX or VxWorks.

2. Enforce segmentation controls and proper network hygiene to mitigate the risk from vulnerable devices. Restrict external communication paths, and isolate or contain vulnerable devices in zones as a mitigating control if they cannot be patched or until they can be patched.

3. Monitor progressive patches released by affected device vendors and devise a remediation plan for your vulnerable asset inventory, balancing business risk and business continuity requirements.

4. Configure devices to rely on internal DNS servers as much as possible and closely monitor external DNS traffic since exploitation requires a malicious DNS server to reply with malicious packets.

5. Monitor all network traffic for malicious packets that try to exploit known vulnerabilities or possible 0-days affecting DNS, mDNS and DHCP clients. Anomalous and malformed traffic should be blocked, or its presence should be at least alerted to network operators. To exploit NAME:WRECK vulnerabilities, an attacker should adopt a similar procedure for any TCP/IP stack. This means that the same detection technique used to identify exploitation of NAME:WRECK will also work to detect exploitation on other TCP/IP stacks and products that we could not yet analyze. In addition, Forescout eyeInspect customers that enabled the threat detection SD script delivered as part of AMNESIA:33 can detect exploitation of NAME:WRECK.

For more information, visit our NAME:WRECK resources page

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Microsoft has released April security updates for vulnerabilities found in: Exchange Server 2013 Exchange Server 2016 Exchange Server 2019

Microsoft has released security updates: Exchange Server 2013,  Exchange Server 2016,  Exchange Server 2019

Vulnerabilities addressed in the April 2021 security updates were responsibly reported to Microsoft by a security partner. Although we are not aware of any active exploits in the wild, our recommendation is to install these updates immediately to protect your environment.

These vulnerabilities affect Microsoft Exchange Server. Exchange Online customers are already protected and do not need to take any action.

For additional information, please see the Microsoft Security Response Center (MSRC) blog. More details about specific CVEs can be found in Security Update Guide (filter on Exchange Server under Product Family).

Forr details go here

Released: April 2021 Exchange Server Security Updates - Microsoft Tech Community

Microsoft Security Blogs Posts

Title: Secure unmanaged devices with Microsoft Defender for Endpoint now
URL: https://www.microsoft.com/security/blog/2021/04/13/secure-unmanaged-devices-with-microsoft-defender-for-endpoint-now/
Date Published (MM/dd/YYYY): 04/13/2021

New Microsoft Defender for Endpoint capabilities let organizations discover and secure unmanaged workstations, mobile devices, servers, and network devices.

Title: Network device discovery and vulnerability assessments
URL: https://techcommunity.microsoft.com/t5/microsoft-defender-for-endpoint/network-device-discovery-and-vulnerability-assessments/ba-p/2267548
Published On

Title: Configuring exclusions for Splunk on RedHat Linux 7.9
URL: https://techcommunity.microsoft.com/t5/microsoft-defender-for-endpoint/configuring-exclusions-for-splunk-on-redhat-linux-7-9/ba-p/2261914
Published On (YYYY-dd-MM):2021-13-04


Several customers have approached me on how to configure Splunk antivirus exclusions for processes, folders, and files within Microsoft Defender for Endpoint on RedHat Enterprise Linux.  This quick reference article has been created to address this common question.

\Title: How far have we come? The evolution of securing identities

URL: https://www.microsoft.com/security/blog/2021/04/13/how-far-have-we-come-the-evolution-of-securing-identities/
Date Published (MM/dd/YYYY): 04/13/2021

What are today’s biggest identity challenges? Have I Been Pwned Founder Troy Hunt talks with Microsoft about the current state of identity

Title: What’s new: Incident timeline
URL: https://techcommunity.microsoft.com/t5/azure-sentinel/what-s-new-incident-timeline/ba-p/2267683
Published On (MM/dd/yyyy): 04/13/2021

Building a timeline of a cyber security incident is one of the most critical parts of affective incident investigation and response. It is essential in order to understand the path of the attack, its scope and to determine appropriate response measures.


Now in public preview, we are redesigning the Azure Sentinel full incident page to display the alerts and bookmarks that are part of the incident in a chronological order. As more alerts are added to the incident, and as more bookmarks are added by analysts, the timeline will update to reflect the information known on the incidents.

New Microsoft Defender for Enpoint blog: Endpoint Discovery - Navigating your way through unmanaged devices


Title: Endpoint Discovery - Navigating your way through unmanaged devices
URL: https://techcommunity.microsoft.com/t5/microsoft-defender-for-endpoint/endpoint-discovery-navigating-your-way-through-unmanaged-devices/ba-p/2248909
Published On (YYYY-dd-MM):2021-13-04

Earlier today, we announced a new set of capabilities for Microsoft Defender for Endpoint that empower organizations to discover and secure network devices and unmanaged endpoints. This is especially critical in the new global hybrid working environment, which exposes the most challenging cybersecurity landscape we’ve ever encountered. This blog provides more information on the unmanaged endpoint discovery feature while an additional blog provides more information on how to configure the network device discovery feature.


The challenge – unmanaged endpoints

In recent years, the efficacy of Endpoint Protection (EPP) and Endpoint Detection and Response (EDR) platforms has continued to increase. With the rise of unified SIEM and XDR (extended detection and response) solutions, like Microsoft 365 Defender, the level of efficacy that our customers are benefiting from continues to improve. To fully utilize these solutions to defend your environment, it's critical to have full visibility of all the devices in your organization. You can't protect what you can't see!


David Weston, Microsoft Director of Enterprise and OS Security, advises:   


“The riskiest threat is the one you don’t know about. Unmanaged devices are literally one of your weakest links. Smart attackers go there first. With work-from-home, the threat has grown exponentially, making discovering and applying security controls to these devices mission critical.” 


There have been many examples where unmanaged devices were exploited and led to a breach, such as the Equifax breach. In this case the breach originated via an unpatched vulnerability on an internet-facing server. This might have been easily addressed except for the fact that the server was unmanaged--no one knew it needed patching. Those responsible for the security profiles and policies of these devices were basically unaware of its existence. 


Unmanaged endpoint discovery in Microsoft Defender for Endpoint

To address scenarios like this we’re adding unmanaged endpoint discovery to Microsoft Defender for Endpoint to help customers discover and secure unmanaged endpoints on their corporate network. This will help detect and report upon any device seen on a corporate network that can be onboarded and secured by Microsoft Defender for Endpoint.


As part of this new functionality, two forms of discovery are provided including Standard and Basic. For public preview all tenants will initially have Basic discovery configured which uses unicast or broadcast network events captured by the onboarded devices to discover unmanaged endpoints. Basic discovery uses the SenseNDR.exe binary for passive network data collection and no network traffic will be initiated. On May 10, unless otherwise configured by the tenant, we will automatically switch from Basic to our recommended form of discovery which is called Standard discovery. This is an active discovery method where managed devices actively probe the network to identify unmanaged devices. From here the interfaces on discovered devices are leveraged to collect threat, vulnerability and metadata used for device fingerprinting. Standard discovery builds a deeper more complete picture of the discovered devices than Basic mode and and allows for vulnerability assessments.


When you go to Microsoft 365 security console you will see two new tiles available. The first shows “Devices to onboard” and will present all devices seen in the last 30 days. We also check whether the device has been seen more than just once over a 3-day period. This prevents a recommendation appearing to onboard a device that was plugged onto the network once, then won’t be seen again.




The second tile is “Discovered devices in my network” and will be broken down into device types.




Once discovered, the devices will appear in the Device Inventory. Clicking the button to “View recently discovered devices” will take you straight to where we have a new set of filters available where you can apply criteria relevant to these new devices, as shown in the screenshot below:


ED 01.jpg


This data is then used as part of the security recommendations within threat and vulnerability management. You can go to the Security recommendations  section under Vulnerability management and type “Onboard” into the Search box to see discovered devices eligible for onboarding:



Once you know about these devices, you can start to onboard them into Defender for Endpoint. This empowers you to close the unmanaged endpoint gap in your environment which is an easy target for attackers. By using the remediation options presented as part of the Security Recommendations, you can open a ticket in Microsoft Endpoint Manager to remediate and onboard the device.


Advanced hunting has also been improved to allow you to query these devices and export data with whatever columns you like:



| where Timestamp > ago(7d)

| summarize arg_max(Timestamp, *) by DeviceId

| where OnboardingStatus == 'Can be onboarded'

| distinct Timestamp, Device Name, DeviceId, OSPlatform, OSDistribution, OSVersion, ReportId


“Timestamp” and “ReportId” lets you run this as a custom detection. For example, you could write a rule to generate an alert whenever a device is connected to a certain subnet.


We have also exposed “Onboarding Status” in the API and in the connector for Azure Sentinel, to provide visibility into security tooling you might have in place.


Enabling discovery

You will see that endpoint discovery is enabled on your tenant through a banner that appears in Device inventory . This banner will be available until the automatic switch from Basic to Standard discovery occurs on May 10th, giving you the option to easily spot and switch over to Standard discovery as soon as you are ready.


ED 02.jpg


If you don’t want Standard discovery to be automatically enabled on May 10, you also have the option to go to Device discovery  in settings and select Basic discovery to ensure the automatic change doesn’t occur.


ED 03.jpg


Controlling discovery

Although we recommend using Standard discovery, there may be conditions that justify applying controls to the discovery process. When Standard discovery actively probes the network, it uses two PowerShell scripts. These PowerShell scripts are Microsoft signed, and are executed from the following location: 


C:\ProgramData\Microsoft\Windows Defender Advanced Threat Protection\Downloads\*.ps


If you are using other security tooling in your environment, there is a possibility these scripts could cause alerts to be raised in those tools. To avoid this situation, we suggest adding the path the scripts are run from to the allow list within your tooling. We also provide customization capabilities around which devices will perform Standard discovery and thus run the scripts. When you enable Standard discovery, the default mode is that all managed Windows 10 devices perform this task. To change this you can leverage a tagging feature which enables you to restrict the execution of the Standard discovery process to only certain devices in your environment.


ED 04.jpg


One caveat: we only recognize tags that have been applied to the device through the portal (or via the API). You cannot utilize tags that have been set via the registry on the device.


You may also have situations where devices are set up as honeypots or have certain networks where you have specific monitoring in place. You can exclude these from Standard discovery and can configure this through the Exclusions tab in Device discovery. There, you can specify either a specific IP address or a subnet to exclude from the Standard discovery mode, although we will still gather details of devices through the passive discovery available in Basic discovery.


ED 05.jpg


Discovering the right devices

One important aspect to this functionality is ensuring it discovers the correct devices. You don't want to take your laptop home and then see all your smart devices, TVs, gaming consoles, etc., showing up in the device inventory list. Not only does it clutter the inventory, but there are also privacy implications from discovering personal, at home devices.


The good news: there is built-in logic to prevent this, and a level of control to define what networks this discovery process runs against. The logic was designed to differentiate between corporate networks and non-corporate networks, to avoid discovery of private or public devices not controlled by the organization. Strict conditions are in place to ensure such devices won’t be discovered and presented in the portal.


The system differentiates between corporate and non-corporate networks by correlating common network interfaces identifiers among Microsoft Defender for Endpoint onboarded devices.


To add an extra layer of control, the following screenshot displays the Monitored networks tab within Device discovery settings which makes discovered networks visible and enables you to specifically whether to include or exclude them.


ED 06.jpg 


Disabling…if you really must!

Finally, if you decide that our new endpoint discovery capability isn't for you, a switch is available in the Advanced settings page in the Microsoft Defender Security Center that allows you to disable the feature (under “Endpoints” in the settings in the Microsoft 365 security center) . While this isn’t recommended, we recognize some organizations may require due diligence to be performed before taking advantage of the feature.




We’re excited to offer you this new functionality and thank you for your interest in the unmanaged endpoint discovery feature. You will gain enhanced visibility of your estate, and the power to close down a vector of attack that attackers increasingly take advantage of.


We encourage you to join us in the public preview program. This program lets you test new features in their early phases and captures your feedback that will influence the final product. For those not already enrolled in the program, we encourage you to participate by turning on preview features.


Once enrolled, we welcome your feedback. More information about this feature and our broader range of unmanaged devices capabilities can be found in the Microsoft Defender for Endpoint product documentation.

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