AWS Lambda

An Elastic detection rule identifies when a single AWS identity, using the AWS CLI, performs more than five distinct read-only discovery API calls (such as Describe*, List*, Get*, and Generate*) across various AWS services within a 10-second window, indicating reconnaissance by an adversary using compromised credentials or an exploited EC2 instance to map the AWS infrastructure for potential targets and further exploitation.

Adversaries may modify AWS Lambda function policies via the AddPermission API call, setting the Principal to '*' to enable public invocation, which establishes persistence and creates a covert execution path within an AWS environment.

This threat detection rule identifies initial reconnaissance activities within AWS by flagging an IAM principal's first-time invocation of sensitive discovery APIs, such as GetCallerIdentity, ListUsers, ListBuckets, and DescribeInstances, when the originating IP address is associated with consumer VPNs, high-usage hosting providers, or networks linked to threat groups like TeamPCP, indicating an attacker performing enumeration of cloud resources from a suspicious network origin.

Adversaries can establish persistent, internet-accessible footholds within AWS environments by configuring AWS Lambda function URLs with an authentication type of NONE, allowing unauthenticated invocation directly from the public internet for command and control, data exfiltration, or on-demand code execution.

Adversaries can exploit the creation of AWS Lambda event source mappings to establish stealthy persistence and execution, or to continuously siphon records from event sources like Amazon SQS, Kinesis, DynamoDB, MSK, Kafka, or MQ, by mapping an event source to an attacker-controlled Lambda function, enabling durable execution and data exfiltration without requiring further interactive access.

Adversaries may delete AWS Lambda functions to disrupt business operations, remove evidence of their presence, or impede incident response, an action detectable by monitoring for `DeleteFunction` calls in `aws.cloudtrail` logs and correlating with expected change windows.

This brief identifies the critical risk of an AWS Lambda layer's permission policy being modified, typically via the `AddLayerVersionPermission` API, to grant external AWS accounts, AWS Organizations, or the public access, potentially leading to the leakage of proprietary code or secrets and creating a supply-chain vector for attacker-influenced code execution in downstream functions.

Adversaries may establish a persistent, internet-reachable entry point by creating or updating an AWS Lambda function URL with an authentication type of NONE, allowing unauthenticated invocation for command and control, data exfiltration, or on-demand code execution, thereby bypassing the need for valid AWS credentials.

An adversary can establish persistence and defense evasion by modifying an AWS Lambda function's resource policy via the `AddPermission` API to grant `lambda:InvokeFunction` permissions to a principal in an external AWS account, enabling unauthorized function invocation and potential data exfiltration without altering function code.

Detects the first direct invocation of an AWS Lambda function by a principal within a 14-day period, excluding AWS service invocations, which can indicate adversary lateral movement, credential abuse, or unauthorized data retrieval in AWS environments.

Attackers are abusing stolen AWS execution-role or user credentials to invoke AWS Lambda functions from unusual source networks (ASNs) not previously associated with the legitimate principal, indicating a credential compromise leading to potential unauthorized access or data exfiltration.

Adversaries leverage cross-account access to invoke AWS Lambda functions from a different account than the function owner, enabling code execution or data retrieval, which requires AWS Lambda data event logging to detect.

Detection of IAM API calls that create or empower IAM users and roles, attach policies, or configure instance profiles when the caller is an assumed role session associated with AWS Lambda, potentially indicating privilege escalation or persistence.

Detection of a Lambda layer being added to an existing AWS Lambda function, potentially indicating malicious activity such as persistence, unauthorized code execution, or data interception by an attacker with the ability to modify function configurations.