Splunk Security
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The following analytic identifies a high number of AccessDenied attempts to list AWS Bedrock foundation models. It leverages AWS CloudTrail logs to detect when a user or service experiences multiple failures when calling the ListFoundationModels API. This activity is significant as it may indicate an adversary performing reconnaissance of available AI models after compromising credentials with limited permissions. Repeated failures could suggest brute force attempts to enumerate accessible resources or misconfigured access controls. If confirmed malicious, this could represent early-stage reconnaissance before attempting to access or manipulate Bedrock models or knowledge bases.
The following analytic detects the use of the 'chown' command to change a file owner to 'root' on a Linux system. It leverages Linux Auditd telemetry, specifically monitoring command-line executions and process details. This activity is significant as it may indicate an attempt to escalate privileges by adversaries, malware, or red teamers. If confirmed malicious, this action could allow an attacker to gain root-level access, leading to full control over the compromised host and potential persistence within the environment.
The following analytic identifies excessive AccessDenied events within an hour timeframe for IAM users in AWS. It leverages AWS CloudTrail logs to detect multiple failed access attempts from the same source IP and user identity. This activity is significant as it may indicate that an access key has been compromised and is being misused for unauthorized discovery actions. If confirmed malicious, this could allow attackers to gather information about the AWS environment, potentially leading to further exploitation or privilege escalation.
This detection identifies when a new Microsoft Intune device health script has been added, updated, or deleted. Intune device remediation scripts can be used by administrators for remote device management, but this functionality can also be abused for SYSTEM-level code execution and lateral movement to Intune-managed devices.
This analytic identifies the invitation of an external guest user within Azure AD. With Azure AD B2B collaboration, users and administrators can invite external users to collaborate with internal users. External guest account invitations should be monitored by security teams as they could potentially lead to unauthorized access. An example of this attack vector was described at BlackHat 2022 by security researcher Dirk-Jan during his talk `Backdooring and Hijacking Azure AD Accounts by Abusing External Identities`. This detection leverages the Universal Audit Log (UAL)/o365:management:activity sourcetype as a detection data source.
The following analytic detects the addition of permissions required for a DCSync attack, specifically DS-Replication-Get-Changes, DS-Replication-Get-Changes-All, and DS-Replication-Get-Changes-In-Filtered-Set. It leverages EventCode 5136 from the Windows Security Event Log to identify when these permissions are granted. This activity is significant because it indicates potential preparation for a DCSync attack, which can be used to replicate AD objects and exfiltrate sensitive data. If confirmed malicious, an attacker could gain extensive access to Active Directory, leading to severe data breaches and privilege escalation.
This analytic detects the creation, deletion, or modification of the "ESX Admins" group in Active Directory. These events may indicate attempts to exploit the VMware ESXi Active Directory Integration Authentication Bypass vulnerability (CVE-2024-37085).
The analytic detects attempts to authenticate using the built-in local Administrator account across more than 30 endpoints within a 5-minute window. It leverages Windows Event Logs, specifically events 4625 (failed logon) and 4624 (successful logon), to identify this behavior. This activity is significant as it may indicate an adversary attempting to validate stolen local credentials across multiple hosts, potentially leading to privilege escalation. If confirmed malicious, this could allow the attacker to gain widespread access and control over numerous systems within the network, posing a severe security risk.
The following analytic detects high-risk sign-in attempts against Azure Active Directory, identified by Azure Identity Protection. It leverages the RiskyUsers and UserRiskEvents log categories from Azure AD events ingested via EventHub. This activity is significant as it indicates potentially compromised accounts, flagged by heuristics and machine learning. If confirmed malicious, attackers could gain unauthorized access to sensitive resources, leading to data breaches or further exploitation within the environment.
This analytic identifies when changes are made to the external guest policies within Azure AD. Specifically, it looks for the "Update policy." operation targeting "B2BManagementPolicy" in the Office 365 Universal Audit Log. The rule extracts and highlights the specific changes made to allowed/blocked domains for B2B collaboration, indicating whether domains were added or removed. Monitoring these changes is crucial as modifications to external identity policies can impact unauthorized access, as described in the BlackHat 2022 talk "Backdooring and Hijacking Azure AD Accounts by Abusing External Identities."
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