Detection: High Frequency Copy Of Files In Network Share

Updated Date: 2024-05-26 ID: 40925f12-4709-11ec-bb43-acde48001122 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects a high frequency of file copying or moving within network shares, which may indicate potential data sabotage or exfiltration attempts. It leverages Windows Security Event Logs (EventCode 5145) to monitor access to specific file types and network shares. This activity is significant as it can reveal insider threats attempting to transfer classified or internal files, potentially leading to data breaches or evidence tampering. If confirmed malicious, this behavior could result in unauthorized data access, data loss, or compromised sensitive information.

Search

1`wineventlog_security` EventCode=5145 RelativeTargetName IN ("*.doc","*.docx","*.xls","*.xlsx","*.ppt","*.pptx","*.log","*.txt","*.db","*.7z","*.zip","*.rar","*.tar","*.gz","*.jpg","*.gif","*.png","*.bmp","*.pdf","*.rtf","*.key") ObjectType=File ShareName IN ("\\\\*\\C$","\\\\*\\IPC$","\\\\*\\admin$") AccessMask= "0x2" 
2|  bucket _time span=5m 
3| stats values(RelativeTargetName) as valRelativeTargetName, values(ShareName) as valShareName, values(ObjectType) as valObjectType, values(AccessMask) as valAccessmask, values(src_port) as valSrcPort, values(SourceAddress) as valSrcAddress count as numShareName by dest, _time, EventCode, src_user, src_ip 
4| eventstats avg(numShareName) as avgShareName, stdev(numShareName) as stdShareName, count as numSlots by dest, _time, EventCode, src_user 
5|  eval upperThreshold=(avgShareName + stdShareName *3) 
6|  eval isOutlier=if(avgShareName > 20 and avgShareName >= upperThreshold, 1, 0) 
7|  search isOutlier=1  
8| `high_frequency_copy_of_files_in_network_share_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Windows Event Log Security 5145	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Security'`	N/A

Macros Used

Name	Value
wineventlog_security	`eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security`
high_frequency_copy_of_files_in_network_share_filter	`search *`

high_frequency_copy_of_files_in_network_share_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
T1537	Transfer Data to Cloud Account	Exfiltration

KillChainPhase.ACTIONS_ON_OBJECTIVES

NistCategory.DE_AE

Cis18Value.CIS_10

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

This behavior may seen in normal transfer of file within network if network share is common place for sharing documents.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
High frequency copy of document into a network share from $src_ip$ by $src_user$	9	30	30

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

References

https://attack.mitre.org/techniques/T1537/

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Security`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Security`	`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: 3