Disable Defender BlockAtFirstSeen Feature
Description
The following analytic detects the modification of the Windows registry to disable the Windows Defender BlockAtFirstSeen feature. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the registry path associated with Windows Defender SpyNet and the DisableBlockAtFirstSeen value. This activity is significant because disabling this feature can allow malicious files to bypass initial detection by Windows Defender, increasing the risk of malware infection. If confirmed malicious, this action could enable attackers to execute malicious code undetected, leading to potential system compromise and data breaches.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2024-05-22
- Author: Steven Dick, Teoderick Contreras, Splunk
- ID: 2dd719ac-3021-11ec-97b4-acde48001122
Annotations
ATT&CK
Kill Chain Phase
- Exploitation
NIST
- DE.CM
CIS20
- CIS 10
CVE
Search
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| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path = "*\\Microsoft\\Windows Defender\\SpyNet*" Registry.registry_value_name = DisableBlockAtFirstSeen Registry.registry_value_data = 0x00000001) BY _time span=1h Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid Registry.user Registry.dest
| `drop_dm_object_name(Registry)`
| where isnotnull(registry_value_data)
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `disable_defender_blockatfirstseen_feature_filter`
Macros
The SPL above uses the following Macros:
disable_defender_blockatfirstseen_feature_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required fields
List of fields required to use this analytic.
- _time
- Registry.dest
- Registry.registry_value_name
- Registry.registry_key_name
- Registry.registry_path
- Registry.registry_value_data
- Registry.process_guid
How To Implement
To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the offical Sysmon TA. https://splunkbase.splunk.com/app/5709
Known False Positives
admin or user may choose to disable windows defender product
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
49.0 | 70 | 70 | modified/added/deleted registry entry $registry_path$ in $dest$ |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
Reference
Test Dataset
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
source | version: 5