ID | Technique | Tactic |
---|---|---|
T1498 | Network Denial of Service | Impact |
Detection: Splunk DoS via Malformed S2S Request
Description
The following analytic identifies attempts to exploit a Denial of Service (DoS) vulnerability in the Splunk-to-Splunk (S2S) protocol by detecting malformed S2S requests. It leverages splunkd
logs, specifically looking for "ERROR" level logs from the "TcpInputProc" component with the thread name "FwdDataReceiverThread" and the message "Invalid _meta atom." This activity is significant as it targets a known vulnerability that could disrupt Splunk services. If confirmed malicious, this could lead to service outages, impacting the availability and reliability of Splunk for monitoring and analysis.
Search
1`splunkd` log_level="ERROR" component="TcpInputProc" thread_name="FwdDataReceiverThread" "Invalid _meta atom"
2| table host, src
3| `splunk_dos_via_malformed_s2s_request_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Splunk | Splunk | 'splunkd_ui_access' |
'splunkd_ui_access.log' |
N/A |
Macros Used
Name | Value |
---|---|
splunkd | index=_internal sourcetype=splunkd |
splunk_dos_via_malformed_s2s_request_filter | search * |
splunk_dos_via_malformed_s2s_request_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
Implementation
This detection does not require you to ingest any new data. The detection does require the ability to search the _internal index. This detection will only find attempted exploitation on versions of Splunk already patched for CVE-2021-3422.
Known False Positives
None.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
An attempt to exploit CVE-2021-3422 was detected from $src$ against $host$ | 50 | 50 | 100 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | /opt/splunk/var/log/splunk/splunkd.log |
splunkd |
Integration | ✅ Passing | Dataset | /opt/splunk/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: 3