Detection: Splunk Endpoint Denial of Service DoS Zip Bomb

Updated Date: 2024-05-27 ID: b237d393-2f57-4531-aad7-ad3c17c8b041 Author: Marissa Bower, Rod Soto, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies crashes in the Splunk search app caused by specially crafted ZIP files, affecting Universal Forwarder versions 8.1.11 and 8.2 versions below 8.2.7.1. It detects this activity by monitoring Universal Forwarder error logs for specific messages indicating invalid or binary file issues. This activity is significant because it can disrupt Splunk operations, leading to potential data loss or monitoring gaps. If confirmed malicious, this attack could result in a denial of service, hindering the organization's ability to monitor and respond to other security incidents effectively.

1`splunkd` component=FileClassifierManager event_message=*invalid* event_message=*binary* 
2|stats count by host component event_message 
3| `splunk_endpoint_denial_of_service_dos_zip_bomb_filter`

Data Source

Name Platform Sourcetype Source Supported App
Splunk Splunk icon Splunk 'splunkd_ui_access' 'splunkd_ui_access.log' N/A

Macros Used

Name Value
splunkd index=_internal sourcetype=splunkd
splunk_endpoint_denial_of_service_dos_zip_bomb_filter search *
splunk_endpoint_denial_of_service_dos_zip_bomb_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
T1499 Endpoint Denial of Service Impact
KillChainPhase.ACTIONS_ON_OBJECTIVES
NistCategory.DE_CM
Cis18Value.CIS_10
Sandworm Team

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

Need to monitor Splunkd data from Universal Forwarders.

Known False Positives

This search may reveal non malicious zip files causing errors as well.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Potential exposure of environment variables from url embedded in dashboard 75 100 75
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 /opt/splunkforwarder/var/log/splunk/splunkd.log splunkd
Integration ✅ Passing Dataset /opt/splunkforwarder/var/log/splunk/splunkd.log splunkd

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