Office — CraftedSignal Threat Feed

Suspicious Process Creation Followed by Memory Access from Unknown Region

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

This detection identifies potential process injection attempts, specifically process hollowing, by monitoring process creation events followed by memory access from unknown regions. The rule focuses on processes spawned by Microsoft Office applications (winword.exe, excel.exe, outlook.exe, powerpnt.exe), scripting engines (cscript.exe, wscript.exe, mshta.exe), and command-line tools (cmd.exe, powershell.exe, rundll32.exe, regsvr32.exe, wmic.exe, cmstp.exe, msxsl.exe). The logic looks for a spawned process by one of these applications/tools, followed by a process access event for an unknown memory region by the parent process, indicating a potential code injection attempt. Attackers use process injection to hide malicious activity within legitimate processes, evading detection and hindering forensic analysis. This technique is a common tactic used to establish persistence, escalate privileges, or execute malicious payloads.

Attack Chain

A user opens a malicious document or executes a script.
The Microsoft Office application (e.g., winword.exe) or scripting engine (e.g., wscript.exe) starts as a parent process.
The parent process creates a new child process (e.g., a legitimate system executable).
The attacker injects malicious code into the newly created child process’s memory, often overwriting legitimate code sections.
The parent process accesses the child process’s memory from an unknown code region, indicating the injected code. Sysmon event ID 10 captures this access.
The injected code executes within the context of the child process, performing malicious actions.
These actions can include establishing persistence, downloading additional malware, or exfiltrating data.

Impact

Successful process injection allows attackers to mask their malicious activities within legitimate processes, making detection and attribution significantly harder. This can lead to prolonged infections, data breaches, and system compromise. The impact can range from individual workstation compromise to widespread organizational damage, depending on the attacker’s objectives and the compromised system’s role. The rule mitigates risks associated with advanced persistent threats (APTs) and commodity malware using process injection for defense evasion.

Recommendation

Enable Sysmon Event ID 1 (Process Creation) and Event ID 10 (Process Access) to collect the necessary telemetry for this detection (Sysmon Event ID 1 - Process Creation, Sysmon Event ID 10 - Process Access).
Deploy the Sigma rule “Suspicious Process Creation CallTrace” to your SIEM and tune for your environment.
Investigate any alerts triggered by the Sigma rule, focusing on the process execution chain and potential malicious activities performed by the injected code.
Consider memory dumping the child process for further analysis, to examine if malicious code exists.

Windows Scheduled Task Creation for Persistence

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

Adversaries frequently leverage scheduled tasks in Windows to maintain persistence, elevate privileges, or facilitate lateral movement within a compromised network. This technique involves creating or modifying scheduled tasks to execute malicious code at specific times or intervals. The detection rule focuses on identifying the creation of new scheduled tasks logged in Windows event logs, filtering out tasks created by system accounts and those associated with legitimate software to minimize false positives. This detection is crucial because successful exploitation allows attackers to execute arbitrary commands or programs on a recurring basis, maintaining a foothold even after system reboots or user logoffs. Defenders need to monitor for anomalous task creation events to identify potential malicious activity. The rule references Microsoft Event ID 4698 as a key data source for detecting scheduled task creation.

Attack Chain

Initial Access: An attacker gains initial access to the system through phishing, exploiting a vulnerability, or using compromised credentials.
Privilege Escalation (if needed): The attacker escalates privileges using exploits or by abusing misconfigurations to gain the necessary permissions to create scheduled tasks.
Task Creation: The attacker creates a new scheduled task using tools like schtasks.exe or PowerShell.
Configuration: The attacker configures the task to execute a malicious script or program at a specific time or event trigger.
Persistence: The scheduled task is configured to run at regular intervals or upon system startup, ensuring persistent access to the compromised system.
Execution: When the scheduled task triggers, the malicious payload executes, performing actions such as installing malware, stealing data, or establishing a command and control connection.
Lateral Movement (optional): The attacker uses the compromised system and scheduled task to move laterally to other systems on the network, repeating the task creation process.

Impact

Successful exploitation via scheduled task creation can lead to persistent access within the compromised environment. The attacker can maintain a foothold even after system restarts, enabling them to perform data exfiltration, deploy ransomware, or cause other disruptive activities. While the risk score is relatively low, the potential for persistence makes this a critical area to monitor, especially in environments where lateral movement is a significant concern. The number of affected systems depends on the scope of the initial compromise and the attacker’s ability to move laterally.

Recommendation

Enable “Audit Other Object Access Events” to generate the necessary Windows Security Event Logs for detecting scheduled task creation (reference: setup instructions in the original rule).
Deploy the provided Sigma rules to your SIEM to detect suspicious scheduled task creation events, and tune the rules by adding exclusions for known benign tasks in your environment.
Review the investigation steps outlined in the rule’s notes to triage alerts related to scheduled task creation, focusing on unfamiliar task names, unusual user accounts, and suspicious scheduled actions.
Use the references URL to understand the specific details of Windows Event ID 4698, which is generated when a scheduled task is created.

Detecting Suspicious Scheduled Task Creation in Windows

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

Adversaries frequently abuse Windows scheduled tasks to establish persistence, move laterally within a network, and escalate privileges. This technique involves creating or modifying scheduled tasks to execute malicious code at specific times or in response to certain events. This detection rule identifies suspicious task creation by filtering out benign tasks and those initiated by system accounts, focusing on potential threats. The rule relies on Windows Security Event Logs, offering a valuable method for identifying unauthorized task creation indicative of malicious activity. The detection logic specifically excludes common tasks associated with software updates from vendors like Hewlett-Packard, Microsoft, Google, and Mozilla, as well as tasks run by system accounts.

Attack Chain

An attacker gains initial access to a system, potentially through phishing or exploiting a vulnerability.
The attacker uses their initial access to execute commands, potentially leveraging PowerShell or cmd.exe.
The attacker uses the schtasks command-line utility or the COM interface to create a new scheduled task.
The scheduled task is configured to execute a malicious payload, such as a reverse shell or a data exfiltration script.
The task is set to trigger based on a specific schedule, such as at system startup, at a specific time, or upon a specific event.
When the trigger occurs, the scheduled task executes the malicious payload.
The malicious payload establishes persistence, allowing the attacker to maintain access to the compromised system.
The attacker can then use the persistent access to move laterally to other systems or to exfiltrate sensitive data.

Impact

Successful exploitation allows adversaries to maintain persistent access to compromised systems, potentially leading to data theft, system disruption, or further lateral movement within the network. By creating malicious scheduled tasks, attackers can ensure their code is executed even after a system reboot or user logoff. This can result in long-term compromise and significant damage to affected organizations. While the number of victims and specific sectors targeted are not detailed, the potential impact is broad due to the widespread use of Windows systems in enterprise environments.

Recommendation

Enable Windows Security Event Logging and ensure that event ID 4698 (A scheduled task was created) is collected.
Deploy the Sigma rule “Suspicious Scheduled Task Creation via Winlog” to your SIEM to detect potentially malicious scheduled task creation events.
Regularly review and update the exclusion list in the Sigma rule to account for new benign scheduled tasks in your environment.
Investigate any alerts generated by the Sigma rule by examining the task’s name, path, actions, and triggers to determine if they are suspicious.
Monitor for related suspicious activity, such as unusual process executions or network connections originating from the compromised system.