Detection: LOLBAS Network Connection On Uncommon Port

Updated Date: 2026-08-24 ID: a6628e6d-be28-4278-b17d-6b5a32968eea Author: Steven Dick, Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic identifies Living Off the Land Binaries and Scripts (LOLBAS) that can legitimately initiate public network connections but are communicating over uncommon destination ports. It leverages the Network Traffic data model and applies per-binary common-port exclusions to reduce false positives while preserving suspicious non-standard communication. This behavior may indicate payload download, command-and-control, proxy execution, or attempts to blend malicious traffic into trusted Windows binaries. Join this detection with the Process Execution events to provide context and avoid false positives.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Network_Traffic.All_Traffic where
 7
 8All_Traffic.app IN (
 9    "*\\bitsadmin.exe",
10    "*\\certutil.exe",
11    "*\\cmstp.exe",
12    "*\\cscript.exe",
13    "*\\ftp.exe",
14    "*\\hh.exe",
15    "*\\ie4uinit.exe",
16    "*\\ieexec.exe",
17    "*\\msbuild.exe",
18    "*\\msdt.exe",
19    "*\\mshta.exe",
20    "*\\msiexec.exe",
21    "*\\presentationhost.exe",
22    "*\\settingsynchost.exe",
23    "*\\syncappvpublishingserver.exe",
24    "*\\workfolders.exe",
25    "*\\wscript.exe",
26    "*\\wuauclt.exe"
27    )
28
29NOT All_Traffic.dest_ip IN (
30        "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16",
31        "100.64.0.0/10", "127.0.0.0/8", "169.254.0.0/16",
32        "192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32",
33        "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32",
34        "192.0.0.171/32", "192.0.2.0/24", "192.31.196.0/24",
35        "192.52.193.0/24", "192.88.99.0/24", "224.0.0.0/4",
36        "192.175.48.0/24", "198.18.0.0/15", "198.51.100.0/24",
37        "203.0.113.0/24", "240.0.0.0/4"
38    )
39
40NOT (
41        (
42            All_Traffic.app IN (
43                "*\\cscript.exe",
44                "*\\wscript.exe"
45            )
46            All_Traffic.dest_port IN ("80", "443", "3128")
47        )
48        OR
49        (
50            All_Traffic.app="*\\ftp.exe"
51            All_Traffic.dest_port IN ("20", "21", "989", "990")
52        )
53        OR
54        (
55            All_Traffic.app IN (
56                "*\\bitsadmin.exe",
57                "*\\certutil.exe",
58                "*\\cmstp.exe",
59                "*\\hh.exe",
60                "*\\ieexec.exe",
61                "*\\msbuild.exe",
62                "*\\msdt.exe",
63                "*\\mshta.exe",
64                "*\\msiexec.exe",
65                "*\\presentationhost.exe",
66                "*\\settingsynchost.exe",
67                "*\\syncappvpublishingserver.exe",
68                "*\\workfolders.exe",
69                "*\\wuauclt.exe"
70            )
71            All_Traffic.dest_port IN ("80", "443")
72        )
73        OR
74        (
75            All_Traffic.app IN (
76                "*\\certutil.exe",
77                "*\\ie4uinit.exe"
78            )
79            All_Traffic.dest_port IN ("389")
80        )
81    )
82
83by All_Traffic.action All_Traffic.app All_Traffic.dest
84   All_Traffic.dest_ip All_Traffic.dest_port
85   All_Traffic.direction All_Traffic.dvc All_Traffic.protocol
86   All_Traffic.protocol_version All_Traffic.src
87   All_Traffic.src_ip All_Traffic.src_port
88   All_Traffic.transport All_Traffic.user
89   All_Traffic.vendor_product
90
91
92| `drop_dm_object_name(All_Traffic)`
93
94| `security_content_ctime(firstTime)`
95
96| `security_content_ctime(lastTime)`
97
98| `lolbas_network_connection_on_uncommon_port_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 3	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
lolbas_network_connection_on_uncommon_port_filter	`search *`

lolbas_network_connection_on_uncommon_port_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
T1105	Ingress Tool Transfer	Command and Control
T1218	System Binary Proxy Execution	Stealth
T1567	Exfiltration Over Web Service	Exfiltration

Actions on Objectives

Exploitation

Command and Control

DE.AE

CIS 13

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 Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

Implementation

To successfully implement this detection you must ingest events into the Network Traffic data model that contain the source, destination, destination port, and communicating process name in the app field. Sysmon EventID 3 is a common source for this data when normalized into the Network Traffic data model.

Known False Positives

Legitimate software installation, support tooling, scripting, synchronization, or update workflows may still use uncommon ports in some environments. Tune approved destinations, ports, and process paths with the analytic filter macro.

Associated Analytic Story

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
LOLBAS process [$app$] on [$src$] connected to public destination [$dest_ip$] over uncommon port [$dest_port$].	dest	system	20

Threat Objects

Field	Type
dest_ip	ip_address
app	process_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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