Enable Host Network Discovery via Netsh

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Identifies use of the netsh.exe program to enable host discovery via the network. Attackers can use this command-line tool to weaken the host firewall settings.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Defense Evasion

Version: 4 (version history)

Added (Elastic Stack release): 7.14.0

Last modified (Elastic Stack release): 8.3.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Host Windows Firewall planned system administration changes.

Investigation guide

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## Triage and analysis

### Investigating Enable Host Network Discovery via Netsh

The Windows Defender Firewall is a native component that provides host-based, two-way network traffic filtering for a
device and blocks unauthorized network traffic flowing into or out of the local device.

Attackers can enable Network Discovery on the Windows firewall to find other systems present in the same network. Systems
with this setting enabled will communicate with other systems using broadcast messages, which can be used to identify
targets for lateral movement. This rule looks for the setup of this setting using the netsh utility.

#### Possible investigation steps

- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Identify the user account that performed the action and whether it should perform this kind of action.
- Contact the account owner and confirm whether they are aware of this activity.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Inspect the host for suspicious or abnormal behaviors in the alert timeframe.

### False positive analysis

- This mechanism can be used legitimately. Analysts can dismiss the alert if the administrator is aware of the activity
and there are justifications for this configuration.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved hosts to prevent further post-compromise behavior.
- Disable Network Discovery:
    - Using netsh: `netsh advfirewall firewall set rule group="Network Discovery" new enable=No`
- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
systems, and web services.
- Review the privileges assigned to the involved users to ensure that the least privilege principle is being followed.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).

## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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process where event.type == "start" and process.name : "netsh.exe" and
process.args : ("firewall", "advfirewall") and process.args :
"group=Network Discovery" and process.args : "enable=Yes"

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 4 (8.3.0 release)
  • Formatting only
Version 3 (8.2.0 release)
  • Formatting only
Version 2 (7.16.0 release)
  • Formatting only