Detection: Windows RDP Cache File Deletion

Updated Date: 2025-07-30 ID: f3e86ff3-b1f9-4382-8924-6913385f1019 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This detection identifies the deletion of RDP bitmap cache files—specifically .bmc and .bin files—typically stored in the user profile under the Terminal Server Client\Cache directory. These files are created by the native Windows Remote Desktop Client (mstsc.exe) and store graphical elements from remote sessions to improve performance. Deleting these files may indicate an attempt to remove forensic evidence of RDP usage. While rare in legitimate user behavior, this action is commonly associated with defense evasion techniques used by attackers or red teamers who wish to hide traces of interactive remote access. When observed in conjunction with recent logon activity, RDP session indicators, or script execution, this behavior should be treated as potentially malicious. Monitoring for deletion of these files provides valuable visibility into anti-forensic actions that often follow lateral movement or hands-on-keyboard activity.

Search

1`sysmon` EventCode IN ("23", "26") TargetFilename IN ("*\\Terminal Server Client\\Cache\\*.bmc", "*\\Terminal Server Client\\Cache\\cache*.bin") 
2| stats count min(_time) as firstTime, max(_time) as lastTime by action dest dvc file_path file_hash file_name file_modify_time process_exec process_guid process_id process_name process_path signature signature_id user user_id vendor_product 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `windows_rdp_cache_file_deletion_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 23	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`
Sysmon EventID 26	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

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

windows_rdp_cache_file_deletion_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
T1070.004	File Deletion	Defense Evasion

Exploitation

DE.AE

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 must ingest logs that include the process name, TargetFilename, and ProcessID executions from your endpoints. If you are utilizing Sysmon, ensure you have at least version 2.0 of the Sysmon TA installed.

Known False Positives

False positives will be present, filter as needed or restrict to critical assets on the perimeter.

Associated Analytic Story

Windows RDP Artifacts and Defense Evasion

Risk Based Analytics (RBA)

Risk Message:

a file related to rdp connection cached has been deleted on $dest$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	40	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