Detection rules › Splunk
Executable File Written in Administrative SMB Share
The following analytic detects executable files (.exe or .dll) being written to Windows administrative SMB shares (Admin$, IPC$, C$). It leverages Windows Security Event Logs with EventCode 5145 to identify this activity. This behavior is significant as it is commonly used by tools like PsExec/PaExec for staging binaries before creating and starting services on remote endpoints, a technique often employed for lateral movement and remote code execution. If confirmed malicious, this activity could allow an attacker to execute arbitrary code remotely, potentially compromising additional systems within the network.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Lateral Movement | T1021.002 Remote Services: SMB/Windows Admin Shares |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 5145 | A network share object was checked to see whether client can be granted desired access. |
Rule body splunk
name: Executable File Written in Administrative SMB Share
id: f63c34fe-a435-11eb-935a-acde48001122
version: 13
creation_date: '2021-04-26'
modification_date: '2026-05-13'
author: Teoderick Contreras, Mauricio Velazco, Splunk
status: production
type: TTP
description: The following analytic detects executable files (.exe or .dll) being written to Windows administrative SMB shares (Admin$, IPC$, C$). It leverages Windows Security Event Logs with EventCode 5145 to identify this activity. This behavior is significant as it is commonly used by tools like PsExec/PaExec for staging binaries before creating and starting services on remote endpoints, a technique often employed for lateral movement and remote code execution. If confirmed malicious, this activity could allow an attacker to execute arbitrary code remotely, potentially compromising additional systems within the network.
data_source:
- Windows Event Log Security 5145
search: '`wineventlog_security` EventCode=5145 RelativeTargetName IN ("*.exe","*.dll") ObjectType=File ShareName IN ("\\\\*\\C$","\\\\*\\IPC$","\\\\*\\admin$") AccessMask= "0x2" | stats min(_time) as firstTime max(_time) as lastTime count by EventCode ShareName RelativeTargetName ObjectType AccessMask src_user src_port IpAddress dest | `security_content_ctime(firstTime)` | `executable_file_written_in_administrative_smb_share_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting Windows Security Event Logs with 5145 EventCode enabled. The Windows TA is also required. Also enable the object Audit access success/failure in your group policy.
known_false_positives: System Administrators may use looks like PsExec for troubleshooting or administrations tasks. However, this will typically come only from certain users and certain systems that can be added to an allow list.
references:
- https://attack.mitre.org/techniques/T1021/002/
- https://www.rapid7.com/blog/post/2013/03/09/psexec-demystified/
- https://labs.vipre.com/trickbot-and-its-modules/
- https://whitehat.eu/incident-response-case-study-featuring-ryuk-and-trickbot-part-2/
- https://thedfirreport.com/2023/05/22/icedid-macro-ends-in-nokoyawa-ransomware/
drilldown_searches:
- name: View the detection results for - "$src_user$"
search: '%original_detection_search% | search src_user = "$src_user$"'
earliest_offset: $info_min_time$
latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$src_user$"
search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
earliest_offset: 7d
latest_offset: "0"
finding:
title: $src_user$ dropped or created an executable file in known sensitive SMB share. Share name=$ShareName$, Target name=$RelativeTargetName$, and Access mask=$AccessMask$
entity:
field: src_user
type: user
score: 50
analytic_story:
- Active Directory Lateral Movement
- BlackSuit Ransomware
- IcedID
- Prestige Ransomware
- Industroyer2
- Data Destruction
- Graceful Wipe Out Attack
- Compromised Windows Host
- Hermetic Wiper
- Trickbot
- VanHelsing Ransomware
asset_type: Endpoint
mitre_attack_id:
- T1021.002
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
- name: True Positive Test
attack_data:
- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/trickbot/exe_smbshare/windows-xml.log
source: XmlWinEventLog:Security
sourcetype: XmlWinEventLog
test_type: unit
Stages and Predicates
Stage 1: search
`wineventlog_security` EventCode=5145 RelativeTargetName IN ("*.exe","*.dll") ObjectType=File ShareName IN ("\\\\*\\C$","\\\\*\\IPC$","\\\\*\\admin$") AccessMask= "0x2"
Stage 2: stats
| stats min(_time) as firstTime max(_time) as lastTime count by EventCode ShareName RelativeTargetName ObjectType AccessMask src_user src_port IpAddress dest
Stage 3: search
| `security_content_ctime(firstTime)`
Stage 4: search
| `executable_file_written_in_administrative_smb_share_filter`
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
AccessMask | eq |
|
EventCode | eq |
|
ObjectType | eq |
|
RelativeTargetName | in |
|
ShareName | in |
|