Detection: Anomalous usage of 7zip

Updated Date: 2024-08-15 ID: 9364ee8e-a39a-11eb-8f1d-acde48001122 Author: Michael Haag, Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects the execution of 7z.exe, a 7-Zip utility, spawned from rundll32.exe or dllhost.exe. This behavior is identified using Endpoint Detection and Response (EDR) telemetry, focusing on process names and parent processes. This activity is significant as it may indicate an adversary attempting to use 7-Zip for data exfiltration, often by renaming the executable to evade detection. If confirmed malicious, this could lead to unauthorized data archiving and exfiltration, compromising sensitive information and potentially leading to further system exploitation.

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 ("rundll32.exe", "dllhost.exe") Processes.process_name=*7z* by Processes.dest Processes.user Processes.parent_process Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)`
6| `anomalous_usage_of_7zip_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($field$)
anomalous_usage_of_7zip_filter search *
anomalous_usage_of_7zip_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
T1560.001 Archive via Utility Collection
T1560 Archive Collected Data Collection
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
APT1
APT28
APT3
APT33
APT39
APT41
APT5
Akira
Aquatic Panda
BRONZE BUTLER
Chimera
CopyKittens
Earth Lusca
FIN13
FIN8
Fox Kitten
GALLIUM
Gallmaker
HAFNIUM
Ke3chang
Kimsuky
Magic Hound
MuddyWater
Mustang Panda
Sowbug
ToddyCat
Turla
Volt Typhoon
Wizard Spider
menuPass
APT28
APT32
Axiom
Dragonfly
FIN6
Ke3chang
Lazarus Group
Leviathan
LuminousMoth
Patchwork
menuPass

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 should be limited as this behavior is not normal for rundll32.exe or dllhost.exe to spawn and run 7zip.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$. This behavior is indicative of suspicious loading of 7zip. 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: 4