Detection rules › Splunk
Temporary File Executed from Public Folder (Windows Event Log)
The BlackBerry Threat Research and Intelligence Team has detailed several behaviors of threat actors using the RomCom remote access trojan. One indication of unusual activity is the placement of binaries in Temp directories with the extension .tmp which are launched by processes stored in the Public folder. This use case detects processes executing from temporary directories with parent processes located in public folders
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Lateral Movement | T1080 Taint Shared Content |
| Command & Control | T1105 Ingress Tool Transfer |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
id: '28106.51148'
title: Temporary File Executed from Public Folder
description: 'The BlackBerry Threat Research and Intelligence Team has detailed several
behaviors of threat actors using the RomCom remote access trojan. One indication
of unusual activity is the placement of binaries in Temp directories with the extension
.tmp which are launched by processes stored in the Public folder. This use case
detects processes executing from temporary directories with parent processes located
in public folders. -- Threat Actor Association: UNC5812'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) "\\AppData\\Local\\Temp\\" ".tmp" "\\Users\\Public"
".exe" | regex parent_process_path="(?i)\x5cUsers\x5cPublic\x5c\.exe"| regex process_path="(?i)\x5cAppData\x5cLocal\x5cTemp\x5c.+\.tmp"
| table _time, host, user, process, process_*, parent_process_* | bin span=1s |
stats values(*) as * by _time, host '
techniques:
- command-and-control:ingress tool transfer
- lateral-movement:taint shared content
technique_id:
- T1105
- T1080
data_category:
- Windows event logs
references:
- https://www.virustotal.com/gui/file/6d3ab9e729bb03ae8ae3fcd824474c5052a165de6cb4c27334969a542c7b261d/behavior
- https://blogs.blackberry.com/en/2022/10/unattributed-romcom-threat-actor-spoofing-popular-apps-now-hits-ukrainian-militaries
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) "\\AppData\\Local\\Temp\\" ".tmp" "\\Users\\Public" ".exe"
Stage 2: regex
| regex parent_process_path="(?i)\x5cUsers\x5cPublic\x5c\.exe"
Stage 3: regex
| regex process_path="(?i)\x5cAppData\x5cLocal\x5cTemp\x5c.+\.tmp"
Stage 4: table
| table _time, host, user, process, process_*, parent_process_*
Stage 5: bucket
| bin span=1s
Stage 6: stats
| stats values(*) as * by _time, host
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 |
|---|---|---|
EventCode | eq |
|
parent_process_path | regex_match |
|
process_path | regex_match |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>4688<" |
| 1 | "\\AppData\\Local\\Temp\\" |
| 1 | ".tmp" |
| 1 | "\\Users\\Public" |
| 1 | ".exe" |