Detection: Windows Phishing PDF File Executes URL Link

Updated Date: 2024-05-23 ID: 2fa9dec8-9d8e-46d3-96c1-202c06f0e6e1 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects suspicious PDF viewer processes spawning browser application child processes. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and parent process names. This activity is significant as it may indicate a PDF spear-phishing attempt where a malicious URL link is executed, leading to potential payload download. If confirmed malicious, this could allow attackers to execute code, escalate privileges, or persist in the environment by exploiting the user's browser to connect to a malicious site.

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name  IN ("AcroRd32.exe", "FoxitPDFReader.exe") Processes.process_name IN ("firefox.exe", "chrome.exe", "iexplore.exe") by Processes.user Processes.parent_process_name Processes.process_name  Processes.parent_process Processes.process Processes.process_id Processes.dest 
3|`drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_phishing_pdf_file_executes_url_link_filter`

Data Source

Name Platform Sourcetype Source Supported App
CrowdStrike ProcessRollup2 N/A 'crowdstrike:events:sensor' 'crowdstrike' N/A

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_phishing_pdf_file_executes_url_link_filter search *
windows_phishing_pdf_file_executes_url_link_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
T1566.001 Spearphishing Attachment Initial Access
T1566 Phishing Initial Access
KillChainPhase.DELIVERY
NistCategory.DE_AE
Cis18Value.CIS_10
APT-C-36
APT1
APT12
APT19
APT28
APT29
APT30
APT32
APT33
APT37
APT38
APT39
APT41
Ajax Security Team
Andariel
BITTER
BRONZE BUTLER
BlackTech
Cobalt Group
Confucius
DarkHydrus
Darkhotel
Dragonfly
EXOTIC LILY
Elderwood
Ember Bear
FIN4
FIN6
FIN7
FIN8
Ferocious Kitten
Gallmaker
Gamaredon Group
Gorgon Group
Higaisa
Inception
IndigoZebra
Kimsuky
Lazarus Group
LazyScripter
Leviathan
Machete
Malteiro
Mofang
Molerats
MuddyWater
Mustang Panda
Naikon
Nomadic Octopus
OilRig
PLATINUM
Patchwork
RTM
Rancor
Sandworm Team
SideCopy
Sidewinder
Silence
TA2541
TA459
TA505
TA551
The White Company
Threat Group-3390
Tonto Team
Transparent Tribe
Tropic Trooper
WIRTE
Windshift
Wizard Spider
admin@338
menuPass
Axiom
GOLD SOUTHFIELD

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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives in PDF file opened PDF Viewer having legitimate URL link, however filter as needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
a pdf file opened in pdf viewer process $parent_process_name$ has a child process of a browser $process_name$ in $dest$ 64 80 80
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

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: 2