Make different Endpoint Configuration Manager AV policies for different device types and deploy the related policies to the corresponding collections, SQL Server Collection, IIS Server Collection, Restricted Workstation Collection, Standard Workstation Collection
Example of AV Policies for different Servers and Workstation types:
To prevent Cryptojacking attack occurred when an attacker hijacks a victims computer to freely run mining for Cryptocurrency without owner's permission, make sure you configure Defender AV policy with "detection for Potentially Unwanted Application" (PUA) to blockmode.
- In Windows version 1910 and earlier, The default setting (not configured) is equivalent
to disable detection of PUA. In windows 10 version 2004 and later, PUA detection is enable by default.
Example, GPO setting for PUA
- Potentially unwanted applications (PUA) are not considered as viruses, malware
but they might perform actions on endpoints which adversely affect endpoint performance or use.
could be done by GPO, Endpoint Manager (Intune), Endpoint Configuration
You should periodically and randomly conduct testing to find out if your company systems passed all the security tests provided by security industry. One example of the system' security test list is here
Antivirus Exclusion recommendation from Microsoft Defender Team:
Once the malware is already infiltrated to the system without being detected by Antivirus, we need the Cloud Endpoint Detection and Response (EDR) feature to continue detecting the malware based on its activities, lateral movement and its behavior. One of the EDR product is Microsoft Defender for Endpoint (MDE), you could have EDR from other Vendors too.
- You should have a policy to enable Microsoft Defender for Endpoint (MDE) with
EDR in block mode.
- The EDR Onboarding policies could be created and enforced by MEM (Intune) or
Antivirus Exclusion could be helpful or harmful if we set Antivirus to skip the threat in files and process. The common misconception could be named a few.
Exclude process which is the frontline interfaced to threat like MS Word, MS Outlook , Java Engine or Acrobat Reader.
Exclude Cabinet, compress file .zip, .tar, .cab, .7ip from AV Scan, they could contain threat source.
Exclude the User Profile temp folder, System temp folder where the malicious file may locate as its base:
The use of environment variables as a wildcard in exclusion lists is limited to system variables only, do not use user environment variables when adding Microsoft Defender Antivirus folder and process exclusions.
Adding an exclusion for a process means that any file opened by that process will be excluded from real-time scanning. These files will still be scanned by any on-demand or scheduled scans, unless a file or folder exclusion has also been created that exempts them.
Grey Area of Exclusion:
Image files: You can chose to exclude file types, such as .gif, .jpg, .jpeg, .png if your environment has a modern, up-to-date software with a strict update policy to handle any vulnerabilities.
Missing MDE (Microsoft Defender for Endpoint) exclusion
If you need to apply exclusion for threat detected by Defender for Endpoint Cloud Service, use the related exclusion.
Microsoft Defender Antivirus exclusions don't apply to other Microsoft Defender for Endpoint capabilities, including endpoint detection and response (EDR), attack surface reduction (ASR) rules, and controlled folder access.
To exclude files broadly, add them to the Microsoft Defender for Endpoint custom indicators.
To exclude files, folders in MDE
Example of Defender for Endpoint - MDE Exclusion from investigation scans:
> Settings\Automation folder exclusions
> New Folder exclusion
> Add multiple folder exclusions as per our needs:
Default Exclusion on Newer Server Version (2016 and 2019)
On Server 2016, 2019, the automatic exclusion helps in prevention of unwanted CPU spike during real-time scanning, it is additional to your custom exclusion list and it is kind of smart scan with exclusion based on server role such as DNS, AD DS, Hyper-V host, File Server, Print Server, Web Server, etc.
Your Custom exclusions take precedence over automatic exclusions.
Automatic exclusions only apply to Real-time protection (RTP) scanning. Automatic exclusions are not honored during a Full/Quick or On-demand scan.
Custom and duplicate exclusions do not conflict with automatic exclusions.
Microsoft Defender Antivirus uses the Deployment Image Servicing and Management (DISM) tools to determine which roles are installed on your computer and apply the appropriate automatic exclusions.
The Discussion about Antivirus Configuration best practice could not be ended here, it might be our on-going attention and practice. I will continue updating this article based on your feedback.