Detection: ASL AWS EC2 Snapshot Shared Externally

Updated Date: 2024-12-17 ID: 00af8f7f-e004-446b-9bba-2732f717ae27 Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects when an EC2 snapshot is shared publicly by analyzing AWS CloudTrail events. This detection method leverages CloudTrail logs to identify modifications in snapshot permissions, specifically when the snapshot is shared outside the originating AWS account. This activity is significant as it may indicate an attempt to exfiltrate sensitive data stored in the snapshot. If confirmed malicious, an attacker could gain unauthorized access to the snapshot's data, potentially leading to data breaches or further exploitation of the compromised information.

1`amazon_security_lake` api.operation=ModifySnapshotAttribute 
2| spath input=api.request.data path=createVolumePermission.add.items{}.group output=group 
3| search group=all 
4| fillnull 
5| stats count min(_time) as firstTime max(_time) as lastTime by api.operation actor.user.uid actor.user.account.uid http_request.user_agent src_endpoint.ip cloud.region api.request.data 
6| rename actor.user.uid as user, src_endpoint.ip as src_ip, cloud.region as region, http_request.user_agent as user_agent 
7| `security_content_ctime(firstTime)` 
8| `security_content_ctime(lastTime)` 
9| `asl_aws_ec2_snapshot_shared_externally_filter`

Data Source

Name Platform Sourcetype Source
ASL AWS CloudTrail AWS icon AWS 'aws:asl' 'aws_asl'

Macros Used

Name Value
amazon_security_lake sourcetype=aws:asl
asl_aws_ec2_snapshot_shared_externally_filter search *
asl_aws_ec2_snapshot_shared_externally_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
T1537 Transfer Data to Cloud Account Exfiltration
Actions on Objectives
DE.CM
CIS 10
INC Ransom
RedCurl

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

The detection is based on Amazon Security Lake events from Amazon Web Services (AWS), which is a centralized data lake that provides security-related data from AWS services. To use this detection, you must ingest CloudTrail logs from Amazon Security Lake into Splunk. To run this search, ensure that you ingest events using the latest version of Splunk Add-on for Amazon Web Services (https://splunkbase.splunk.com/app/1876) or the Federated Analytics App.

Known False Positives

It is possible that an AWS admin has legitimately shared a snapshot with others for a specific purpose.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

AWS EC2 snapshot from user $user$ is shared publicly by user $user$

Risk Object Risk Object Type Risk Score Threat Objects
user user 48 src_ip

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_asl aws:asl
Integration ✅ Passing Dataset aws_asl aws:asl

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: 1