Allow Inbound Traffic In Firewall Rule

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Description

The following analytic identifies suspicious PowerShell command to allow inbound traffic inbound to a specific local port within the public profile. This technique was seen in some attacker want to have a remote access to a machine by allowing the traffic in firewall rule.

• Type: TTP

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2021-05-19
• Author: Teoderick Contreras, Splunk
• ID: a5d85486-b89c-11eb-8267-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1021.001	Remote Desktop Protocol	Lateral Movement

T1021

Remote Services

Lateral Movement

Kill Chain Phase

• Exploitation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

`powershell` EventCode=4104 Message = "*firewall*" Message = "*Inbound*" Message = "*Allow*"  Message = "*-LocalPort*" 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode Message ComputerName User 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `allow_inbound_traffic_in_firewall_rule_filter`

Macros

The SPL above uses the following Macros:

• powershell
• security_content_ctime

allow_inbound_traffic_in_firewall_rule_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
• EventCode
• Message
• ComputerName
• User

How To Implement

To successfully implement this search, you need to be ingesting logs with the powershell logs from your endpoints. make sure you enable needed registry to monitor this event.

Known False Positives

administrator may allow inbound traffic in certain network or machine.

Associated Analytic Story

• Prohibited Traffic Allowed or Protocol Mismatch

RBA

Risk Score	Impact	Confidence	Message
3.0	10	30	Suspicious firewall modification detected on endpoint $ComputerName$ by user $user$.

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

• https://docs.microsoft.com/en-us/powershell/module/netsecurity/new-netfirewallrule?view=windowsserver2019-ps

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

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