Detection: Internal Horizontal Port Scan NMAP Top 20

Updated Date: 2024-09-25 ID: 3141a041-4f57-4277-9faa-9305ca1f8e5b Author: Dean Luxton Type: TTP Product: Splunk Enterprise Security

Description

This analytic identifies instances where an internal host has attempted to communicate with 250 or more destination IP addresses using on of the NMAP top 20 ports. Horizontal port scans from internal hosts can indicate reconnaissance or scanning activities, potentially signaling malicious intent or misconfiguration. By monitoring network traffic logs, this detection helps detect and respond to such behavior promptly, enhancing network security and preventing potential threats.

Search

 1
 2| tstats `security_content_summariesonly` values(All_Traffic.action) as action values(All_Traffic.src_category) as src_category values(All_Traffic.dest_zone) as dest_zone values(All_Traffic.src_zone) as src_zone count from datamodel=Network_Traffic where All_Traffic.src_ip IN ("10.0.0.0/8","172.16.0.0/12","192.168.0.0/16") AND All_Traffic.dest_port IN (21, 22, 23, 25, 53, 80, 110, 111, 135, 139, 143, 443, 445, 993, 995, 1723, 3306, 3389, 5900, 8080) by All_Traffic.src_ip All_Traffic.dest_port All_Traffic.dest_ip span=1s _time All_Traffic.transport  
 3| `drop_dm_object_name("All_Traffic")`  
 4| eval gtime=_time  
 5| bin span=1h gtime  
 6| stats min(_time) as _time values(action) as action dc(dest_ip) as totalDestIPCount values(src_category) as src_category values(dest_zone) as dest_zone values(src_zone) as src_zone by src_ip dest_port gtime transport  
 7| where totalDestIPCount>=250  
 8| eval dest_port=transport + "/" + dest_port  
 9| stats min(_time) as _time values(action) as action sum(totalDestIPCount) as totalDestIPCount values(src_category) as src_category values(dest_port) as dest_ports values(dest_zone) as dest_zone values(src_zone) as src_zone by src_ip gtime  
10| fields - gtime  
11| `internal_horizontal_port_scan_nmap_top_20_filter`

Data Source

Name	Platform	Sourcetype	Source
AWS CloudWatchLogs VPCflow	AWS	`'aws:cloudwatchlogs:vpcflow'`	`'aws_cloudwatchlogs_vpcflow'`

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
internal_horizontal_port_scan_nmap_top_20_filter	`search *`

internal_horizontal_port_scan_nmap_top_20_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1046	Network Service Discovery	Discovery

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_13

APT32

APT39

APT41

Agrius

BackdoorDiplomacy

BlackTech

Chimera

Cobalt Group

DarkVishnya

Ember Bear

FIN13

FIN6

Fox Kitten

INC Ransom

Lazarus Group

Leafminer

Magic Hound

Naikon

OilRig

RedCurl

Rocke

Suckfly

TeamTNT

Threat Group-3390

Tropic Trooper

Volt Typhoon

menuPass

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To properly run this search, Splunk needs to ingest data from networking telemetry sources such as firewalls, NetFlow, or host-based networking events. Ensure that the Network_Traffic data model is populated to enable this search effectively.

Known False Positives

Unknown

Associated Analytic Story

Network Discovery

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
$src_ip$ has scanned for ports $dest_ports$ across $totalDestIPCount$ destination IPs	72	90	80

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`aws:cloudwatchlogs:vpcflow`	`aws:cloudwatchlogs:vpcflow`
Integration	✅ Passing	Dataset	`aws:cloudwatchlogs:vpcflow`	`aws:cloudwatchlogs:vpcflow`

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: GitHub | Version: 1