Detection rules › Splunk
Symbolic OR Hard File Link Created (PowerShell)
Symbolic links are ways of referencing other files or programs that will be opened or executed when the shortcut is clicked or executed by a system startup process
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Execution | T1204.002 User Execution: Malicious File |
| Persistence | T1547.009 Boot or Logon Autostart Execution: Shortcut Modification |
| Privilege Escalation | T1547.009 Boot or Logon Autostart Execution: Shortcut Modification |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| PowerShell | Event ID 4104 | Creating Scriptblock text (MessageNumber of MessageTotal). |
Rule body yaml
id: '6105.6584'
title: Symbolic OR Hard File Link Created
description: 'Symbolic links are ways of referencing other files or programs that
will be opened or executed when the shortcut is clicked or executed by a system
startup process. -- Threat Actor Association: APT29/Nobelium, APT43, Arid Viper/APT
C-23, Kimsuky, Lancefly, Gamaredon Group/Shuckworm,/Armageddon, SideWinder, TA505,
TA576, UAC-0057 (GhostWriter), UNC2589, UNC4990, Wizard Spider -- Software Association:
Astaroth, Black Basta, Bumblebee, Emotet, MINEBRIDGE, Qakbot/Qbot, Trickbot, Remcos
RAT - #TrendingThreat #Russia #Ukraine - Atomics T1546.008 Test #3'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_powershell` TERM(EventCode=4104) ((("New-Item"
OR TERM(ni)) (TERM(SymbolicLink) OR TERM(hardlink))) OR TERM(mklink)) | table _time,
host, user, process, process_* | bin span=1s | stats values(*) as * by _time, host '
techniques:
- persistence:boot or logon autostart execution:shortcut modification
- privilege-escalation:boot or logon autostart execution:shortcut modification
- execution:user execution:malicious file
technique_id:
- T1547.009
- T1204.002
data_category:
- PowerShell logs
- Process command-line parameters
references:
- https://blog-assets.f-secure.com/wp-content/uploads/2019/10/15163408/BlackEnergy_Quedagh.pdf
- https://www.fireeye.com/blog/threat-research/2019/01/apt39-iranian-cyber-espionage-group-focused-on-personal-information.html
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_powershell` TERM(EventCode=4104) ((("New-Item" OR TERM(ni)) (TERM(SymbolicLink) OR TERM(hardlink))) OR TERM(mklink))
Stage 2: table
| table _time, host, user, process, process_*
Stage 3: bucket
| bin span=1s
Stage 4: 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 |
|
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 | "New-Item" |
| 1 | TERM |
| 1 | ni |
| 1 | TERM |
| 1 | SymbolicLink |
| 1 | TERM |
| 1 | hardlink |
| 1 | TERM |
| 1 | mklink |