Detection: Detect S3 access from a new IP

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-10-17 ID: e6f1bb1b-f441-492b-9126-902acda217da Author: Bhavin Patel, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic identifies access to an S3 bucket from a new or previously unseen remote IP address. It leverages S3 bucket-access logs, specifically focusing on successful access events (http_status=200). This activity is significant because access from unfamiliar IP addresses could indicate unauthorized access or potential data exfiltration attempts. If confirmed malicious, this activity could lead to unauthorized data access, data theft, or further exploitation of the compromised S3 bucket, posing a significant risk to sensitive information stored within the bucket.

 1`aws_s3_accesslogs` http_status=200  [search `aws_s3_accesslogs` http_status=200 
 2| stats earliest(_time) as firstTime latest(_time) as lastTime by bucket_name remote_ip 
 3| inputlookup append=t previously_seen_S3_access_from_remote_ip 
 4| stats min(firstTime) as firstTime, max(lastTime) as lastTime by bucket_name remote_ip 
 5| outputlookup previously_seen_S3_access_from_remote_ip
 6| eval newIP=if(firstTime >= relative_time(now(), "-70m@m"), 1, 0) 
 7| where newIP=1 
 8| `security_content_ctime(firstTime)`
 9| `security_content_ctime(lastTime)` 
10| table bucket_name remote_ip]
11| iplocation remote_ip 
12|rename remote_ip as src_ip 
13| table _time bucket_name src_ip City Country operation request_uri 
14| `detect_s3_access_from_a_new_ip_filter`

Data Source

No data sources specified for this detection.

Macros Used

Name Value
aws_s3_accesslogs sourcetype=aws:s3:accesslogs
detect_s3_access_from_a_new_ip_filter search *
detect_s3_access_from_a_new_ip_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
T1530 Data from Cloud Storage Collection
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_13
Fox Kitten
Scattered Spider

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

You must install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your S3 access logs' inputs. This search works best when you run the "Previously Seen S3 Bucket Access by Remote IP" support search once to create a history of previously seen remote IPs and bucket names.

Known False Positives

S3 buckets can be accessed from any IP, as long as it can make a successful connection. This will be a false postive, since the search is looking for a new IP within the past hour

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
New S3 access from a new IP - $src_ip$ 25 50 50
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation Not Applicable N/A N/A N/A
Unit ❌ Failing N/A N/A N/A
Integration ❌ Failing N/A N/A N/A

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