Configure and validate exclusions for Microsoft Defender for Endpoint on Linux

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10/14/2024

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This article provides information on how to define antivirus and global exclusions for Microsoft Defender for Endpoint. Antivirus exclusions apply to on-demand scans, real-time protection (RTP), and behavior monitoring (BM). Global exclusions apply to real-time protection (RTP), behavior monitoring (BM), and endpoint detection and response (EDR), thus stopping all the associated antivirus detections, EDR alerts, and visibility for the excluded item.

Important

The antivirus exclusions described in this article apply to only antivirus capabilities and not to endpoint detection and response (EDR). Files that you exclude using the antivirus exclusions described in this article can still trigger EDR alerts and other detections. Global exclusions described in this section apply to antivirus and endpoint detection and response capabilities, thus stopping all associated antivirus protection, EDR alerts, and detections. Global exclusions are currently in public preview, and are available in Defender for Endpoint version 101.23092.0012 or later, in the Insiders Slow and Production rings. For EDR exclusions, contact support.

You can exclude certain files, folders, processes, and process-opened files from Defender for Endpoint on Linux.

Exclusions can be useful to avoid incorrect detections on files or software that are unique or customized to your organization. Global exclusions are useful for mitigating performance issues caused by Defender for Endpoint on Linux.

Warning

Defining exclusions lowers the protection offered by Defender for Endpoint on Linux. You should always evaluate the risks that are associated with implementing exclusions, and you should only exclude files that you are confident are not malicious.

Supported exclusion scopes

As described in an earlier section, we support two exclusion scopes: antivirus (epp) and global (global) exclusions.

Antivirus exclusions can be used to exclude trusted files and processes from real-time protection while still having EDR visibility. Global exclusions are applied at sensor level and to mute the events that match exclusion conditions very early in the flow, before any processing is done, thus stopping all EDR alerts and antivirus detections.

Note

Global (global) is a new exclusion scope that we are introducing in addition to antivirus (epp) exclusion scopes that are already supported by Microsoft.

Exclusion Category	Exclusion Scope	Description
Antivirus Exclusion	Antivirus engine (scope: epp)	Excludes content from antivirus (AV) scans and on-demand scans.
Global Exclusion	Antivirus and endpoint detections and response engine (scope: global)	Excludes events from real time protection and EDR visibility. Doesn't apply to on-demand scans by default.

Supported exclusion types

The following table shows the exclusion types supported by Defender for Endpoint on Linux.

Exclusion	Definition	Examples
File extension	All files with the extension, anywhere on the device (not available for global exclusions)	`.test`
File	A specific file identified by the full path	`/var/log/test.log` `/var/log/*.log` `/var/log/install.?.log`
Folder	All files under the specified folder (recursively)	`/var/log/` `/var/*/`
Process	A specific process (specified either by the full path or file name) and all files opened by it	`/bin/cat` `cat` `c?t`

Important

The paths used must be hard links, not symbolic links, in order to be successfully excluded. You can check if a path is a symbolic link by running file <path-name>.

File, folder, and process exclusions support the following wildcards:

Note

File path needs to be present before adding or removing file exclusions with scope as global. Wildcards are not supported while configuring global exclusions.

Wildcard Description Examples

Wildcard	Description	Examples
*	Matches any number of any characters including none (note if this wildcard isn't used at the end of the path then it substitutes only one folder)	`/var//tmp` includes any file in `/var/abc/tmp` and its subdirectories, and `/var/def/tmp` and its subdirectories. It doesn't include `/var/abc/log` or `/var/def/log` `/var//` only includes any files in its subdirectories such as `/var/abc/`, but not files directly inside `/var`.
?	Matches any single character	`file?.log` includes `file1.log` and `file2.log`, but not`file123.log`

Matches any number of any characters including none
(note if this wildcard isn't used at the end of the path then it substitutes only one folder)

/var/*/tmp includes any file in /var/abc/tmp and its subdirectories, and /var/def/tmp and its subdirectories. It doesn't include /var/abc/log or /var/def/log

/var/*/ only includes any files in its subdirectories such as /var/abc/, but not files directly inside /var.

? Matches any single character file?.log includes file1.log and file2.log, but notfile123.log

Note

For antivirus exclusions, when using the * wildcard at the end of the path, it will match all files and subdirectories under the parent of the wildcard.

How to configure the list of exclusions

Using the management console

To configure exclusions from Puppet, Ansible, or another management console, please refer to the following sample mdatp_managed.json.

{
   "exclusionSettings":{
     "exclusions":[
        {
           "$type":"excludedPath",
           "isDirectory":true,
           "path":"/home/*/git<EXAMPLE DO NOT USE>",
           "scopes": [
              "epp"
           ]
        },
        {
           "$type":"excludedPath",
           "isDirectory":true,
           "path":"/run<EXAMPLE DO NOT USE>",
           "scopes": [
              "global"
           ]
        },
        {
           "$type":"excludedPath",
           "isDirectory":false,
           "path":"/var/log/system.log<EXAMPLE DO NOT USE><EXCLUDED IN ALL SCENARIOS>",
           "scopes": [
              "epp", "global"
           ]
        },
        {
           "$type":"excludedFileExtension",
           "extension":".pdf<EXAMPLE DO NOT USE>",
           "scopes": [
              "epp"
           ]
        },
        {
           "$type":"excludedFileName",
           "name":"/bin/cat<EXAMPLE DO NOT USE><NO SCOPE PROVIDED - GLOBAL CONSIDERED>"
        }
     ],
     "mergePolicy":"admin_only"
   }
}

For more information, see Set preferences for Defender for Endpoint on Linux.

Using the command line

Run the following command to see the available switches for managing exclusions:

Note

--scope is an optional flag with accepted value as epp or global. It provides the same scope used while adding the exclusion to remove the same exclusion. In the command line approach, if the scope isn't mentioned, the scope value is set as epp. Exclusions added through CLI before the introduction of --scope flag remain unaffected and their scope is considered epp.

mdatp exclusion

Tip

When configuring exclusions with wildcards, enclose the parameter in double-quotes to prevent globbing.

Examples:

Add an exclusion for a file extension (Extension exclusion isn't supported for global exclusion scope) :

mdatp exclusion extension add --name .txt

Extension exclusion configured successfully

mdatp exclusion extension remove --name .txt

Extension exclusion removed successfully

Add/Remove an exclusion for a file (File path should already be present in case of adding or removing exclusion with global scope) :

mdatp exclusion file add --path /var/log/dummy.log --scope epp

File exclusion configured successfully

mdatp exclusion file remove --path /var/log/dummy.log --scope epp

File exclusion removed successfully"

mdatp exclusion file add --path /var/log/dummy.log --scope global

File exclusion configured successfully

mdatp exclusion file remove --path /var/log/dummy.log --scope global

File exclusion removed successfully"

Add/Remove an exclusion for a folder:

mdatp exclusion folder add --path /var/log/ --scope epp

Folder exclusion configured successfully

mdatp exclusion folder remove --path /var/log/ --scope epp

Folder exclusion removed successfully

  mdatp exclusion folder add --path /var/log/ --scope global

Folder exclusion configured successfully

mdatp exclusion folder remove --path /var/log/ --scope global

Folder exclusion removed successfully

Add an exclusion for a second folder:

mdatp exclusion folder add --path /var/log/ --scope epp
mdatp exclusion folder add --path /other/folder  --scope global

Folder exclusion configured successfully

Add an exclusion for a folder with a wildcard in it:

Note

Wildcards are not supported while configuring global exclusions.
```
mdatp exclusion folder add --path "/var/*/tmp"
```
Note

This will only exclude paths under /var/*/tmp/, but not folders which are siblings of tmp; for example, /var/this-subfolder/tmp, but not /var/this-subfolder/log.
```
mdatp exclusion folder add --path "/var/" --scope epp
```
OR
```
mdatp exclusion folder add --path "/var/*/" --scope epp
```
Note

This will exclude all paths whose parent is /var/; for example, /var/this-subfolder/and-this-subfolder-as-well.
```
Folder exclusion configured successfully
```

Add an exclusion for a process:

mdatp exclusion process add --name /usr/bin/cat --scope global

Process exclusion configured successfully

mdatp exclusion process remove --name /usr/bin/cat  --scope global

Process exclusion removed successfully

  mdatp exclusion process add --name /usr/bin/cat --scope epp

Process exclusion configured successfully

mdatp exclusion process remove --name /usr/bin/cat  --scope epp

Process exclusion removed successfully

Add an exclusion for a second process:

mdatp exclusion process add --name cat --scope epp
mdatp exclusion process add --name dog --scope global

Process exclusion configured successfully

Validate exclusions lists with the EICAR test file

You can validate that your exclusion lists are working by using curl to download a test file.

In the following Bash snippet, replace test.txt with a file that conforms to your exclusion rules. For example, if you have excluded the .testing extension, replace test.txt with test.testing. If you're testing a path, ensure that you run the command within that path.

curl -o test.txt https://secure.eicar.org/eicar.com.txt

If Defender for Endpoint on Linux reports malware, then the rule isn't working. If there's no report of malware, and the downloaded file exists, then the exclusion is working. You can open the file to confirm that the contents are the same as what is described on the EICAR test file website.

If you don't have Internet access, you can create your own EICAR test file. Write the EICAR string to a new text file with the following Bash command:

echo 'X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*' > test.txt

You can also copy the string into a blank text file and attempt to save it with the file name or in the folder you're attempting to exclude.

Allow threats

In addition to excluding certain content from being scanned, you can also configure the product not to detect some classes of threats (identified by the threat name). You should exercise caution when using this functionality, as it can leave your device unprotected.

To add a threat name to the allowed list, execute the following command:

mdatp threat allowed add --name [threat-name]

The threat name associated with a detection on your device can be obtained using the following command:

mdatp threat list

For example, to add EICAR-Test-File (not a virus) (the threat name associated with the EICAR detection) to the allowed list, execute the following command:

mdatp threat allowed add --name "EICAR-Test-File (not a virus)"

Tip

Do you want to learn more? Engage with the Microsoft Security community in our Tech Community: Microsoft Defender for Endpoint Tech Community.

Comhroinn trí

Configure and validate exclusions for Microsoft Defender for Endpoint on Linux

Supported exclusion scopes

Supported exclusion types

How to configure the list of exclusions

Using the management console

Using the command line

Validate exclusions lists with the EICAR test file

Allow threats

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