Amazon Security Lake — CraftedSignal Threat Feed

AWS CloudTrail Logging Stopped for Defense Evasion

hello@craftedsignal.io — Wed, 03 Jan 2024 12:00:00 +0000

This analytic detects StopLogging events within AWS CloudTrail logs, which is a critical action that adversaries may use to evade detection. By halting the logging of their malicious activities, attackers aim to operate undetected within a compromised AWS environment. This detection is achieved by monitoring for specific CloudTrail log entries that indicate the cessation of logging activities. Identifying such behavior is crucial for a Security Operations Center (SOC), as it signals an attempt to undermine the integrity of logging mechanisms, potentially allowing malicious activities to proceed without observation. The impact of this evasion tactic is significant, as it can severely hamper incident response and forensic investigations by obscuring the attacker’s actions. The detection is based on Amazon Security Lake events.

Attack Chain

An attacker gains initial access to an AWS account, potentially through compromised credentials or exploiting a vulnerability.
The attacker enumerates existing CloudTrail configurations to identify the target log trails.
The attacker attempts to disable logging by invoking the StopLogging API call on the CloudTrail service.
The AWS CloudTrail service receives the StopLogging API request.
If the attacker has sufficient privileges, the CloudTrail service processes the request, and logging is stopped for the specified trail.
The attacker performs malicious activities within the AWS environment without those actions being logged by CloudTrail.
The attacker attempts to delete or modify existing CloudTrail log files to further cover their tracks (not directly detected by this analytic, but a likely follow-on action).
The attacker achieves their objective, such as data exfiltration or resource compromise, without immediate detection due to the disabled logging.

Impact

Successful evasion of CloudTrail logging can severely impair incident response and forensic investigations. Without logs, identifying the scope and nature of the attack becomes significantly more challenging. Organizations may experience delayed breach detection, increased dwell time for attackers, and difficulty in recovering compromised resources. The impact can extend to compliance violations, as many regulatory frameworks require comprehensive audit logging. This is a high severity incident because it prevents security teams from understanding what an attacker did in the environment.

Recommendation

Deploy the Sigma rule Detect AWS CloudTrail StopLogging Event to your SIEM and tune for your environment to detect instances where CloudTrail logging is stopped.
Investigate any detected StopLogging events (as surfaced by the Sigma rule) to determine whether they are authorized administrative actions or potentially malicious.
Monitor for unusual API calls and activities originating from the source IP addresses and user accounts identified in the ASL AWS Defense Evasion Stop Logging Cloudtrail search results.
Review and enforce strict IAM policies to minimize the potential for unauthorized users to disable CloudTrail logging to prevent future attempts at defense evasion.
Ingest CloudTrail logs from Amazon Security Lake into Splunk, ensuring you are using the latest version of Splunk Add-on for Amazon Web Services to use the ASL AWS Defense Evasion Stop Logging Cloudtrail search.

AWS Network ACL Created with All Ports Open

hello@craftedsignal.io — Wed, 03 Jan 2024 10:00:00 +0000

This detection focuses on identifying misconfigured AWS Network ACLs (NACLs) that permit unrestricted traffic. AWS NACLs act as a firewall for controlling traffic in and out of subnets within a Virtual Private Cloud (VPC). When an NACL is configured to allow all ports and protocols from any IP address (0.0.0.0/0), it effectively bypasses security controls and exposes resources to potential threats. The activity is detected by monitoring AWS CloudTrail events for CreateNetworkAclEntry or ReplaceNetworkAclEntry API calls. This configuration error can be introduced by administrators during initial setup or through misconfiguration during updates. Defenders should ensure that NACLs follow the principle of least privilege to limit the attack surface.

Attack Chain

An attacker identifies a target AWS environment.
The attacker scans for publicly accessible services or resources.
An administrator, either maliciously or accidentally, creates or modifies a Network ACL using the AWS Management Console, CLI, or API with overly permissive rules (allowing all traffic: ruleAction=allow AND egress=false AND aclProtocol=-1 AND cidrBlock=0.0.0.0/0).
The misconfigured NACL is applied to one or more subnets within the VPC.
The attacker exploits the open ports and protocols to gain unauthorized access.
The attacker attempts to move laterally within the AWS environment.
The attacker exfiltrates sensitive data or disrupts services.

Impact

A misconfigured Network ACL that allows all traffic can have severe consequences. It can lead to unauthorized access to sensitive data, potential data breaches, service disruption, and further compromise of the AWS environment. The impact is particularly high if critical resources are located within the affected subnets. This type of misconfiguration violates security best practices and compliance requirements.

Recommendation

Deploy the Sigma rule AWS Network ACL Created with All Ports Open to your SIEM to detect this specific misconfiguration (logsource: ASL AWS CloudTrail, category: network_connection).
Review existing Network ACL configurations to identify and remediate any overly permissive rules (check AWS console or use AWS CLI/API).
Implement automated checks to validate Network ACL configurations against security best practices.
Ensure that NACLs follow the principle of least privilege by only allowing necessary traffic (review NACL ruleAction, egress, aclProtocol, and cidrBlock settings in CloudTrail logs).
Investigate any identified instances of overly permissive NACL configurations to determine the root cause and potential impact (analyze CloudTrail logs for CreateNetworkAclEntry or ReplaceNetworkAclEntry events).

AWS S3 Bucket Lifecycle Rule for Rapid Log Deletion

hello@craftedsignal.io — Tue, 02 Jan 2024 12:00:00 +0000

This threat involves the modification of AWS S3 bucket lifecycle policies to expedite the deletion of CloudTrail logs. The technique focuses on configuring a lifecycle rule for an S3 bucket with an expiration period of fewer than three days. By shortening the retention period, attackers aim to quickly eliminate CloudTrail logs, thereby covering their tracks and impeding forensic investigations. This activity is significant because it directly targets security logging, a critical component for threat detection and incident response. This technique can be used by various threat actors seeking to evade detection within AWS environments.

Attack Chain

The attacker gains unauthorized access to an AWS account, potentially through compromised credentials or a vulnerability.
The attacker identifies the S3 bucket used to store CloudTrail logs.
The attacker uses AWS CLI or the AWS Management Console to execute the PutBucketLifecycle API call.
The PutBucketLifecycle call modifies the lifecycle configuration of the S3 bucket.
The new lifecycle rule specifies a short expiration period (less than three days) for objects in the bucket.
CloudTrail logs within the S3 bucket are automatically deleted after the specified expiration period.
The attacker’s actions are no longer recorded in CloudTrail, hindering incident response.

Impact

Successful execution of this attack leads to the rapid and irreversible deletion of CloudTrail logs. This can severely hamper incident response efforts, making it difficult to trace attacker actions, identify the scope of a breach, and conduct thorough forensic analysis. Organizations may be unable to meet compliance requirements related to data retention and audit logging.

Recommendation

Deploy the provided Sigma rule to detect suspicious PutBucketLifecycle events with short expiration periods in your SIEM.
Investigate any detected PutBucketLifecycle events modifying S3 bucket lifecycle policies (logsource: ASL AWS CloudTrail).
Monitor AWS CloudTrail logs for unusual API calls related to S3 bucket lifecycle management (logsource: ASL AWS CloudTrail).