| ID | Technique | Tactic |
|---|---|---|
| T1046 | Network Service Discovery | Discovery |
Detection: Internal Vertical Port Scan
Description
This analytic detects instances where an internal host attempts to communicate with over 500 ports on a single destination IP address. It includes filtering criteria to exclude applications performing scans over ephemeral port ranges, focusing on potential reconnaissance or scanning activities. Monitoring network traffic logs allows for timely detection and response to such behavior, enhancing network security by identifying and mitigating potential threats promptly.
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") by All_Traffic.src_ip All_Traffic.dest_port All_Traffic.dest_ip All_Traffic.transport span=1s _time
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(eval(if(dest_port<1024 AND transport="tcp",dest_port,null))) as privilegedDestTcpPortCount dc(eval(if(transport="tcp",dest_port,null))) as totalDestTcpPortCount dc(eval(if(dest_port<1024 AND transport="udp",dest_port,null))) as privilegedDestUdpPortCount dc(eval(if(transport="udp",dest_port,null))) as totalDestUdpPortCount values(src_category) as src_category values(dest_zone) as dest_zone values(src_zone) as src_zone by src_ip dest_ip transport gtime
7| eval totalDestPortCount=totalDestUdpPortCount+totalDestTcpPortCount, privilegedDestPortCount=privilegedDestTcpPortCount+privilegedDestUdpPortCount
8| where (totalDestPortCount>=500 AND privilegedDestPortCount>=20)
9| fields - gtime
10| `internal_vertical_port_scan_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_vertical_port_scan_filter | search * |
internal_vertical_port_scan_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
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
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| $src_ip$ has scanned $totalDestPortCount$ ports on $dest_ip$ | 64 | 80 | 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: 2