Brave — CraftedSignal Threat Feed

Suspicious Child Processes from Communication Applications

hello@craftedsignal.io — Wed, 31 Jan 2024 12:00:00 +0000

This detection rule focuses on identifying suspicious child processes of communication applications such as Slack, Cisco Webex, Microsoft Teams, Discord, WhatsApp, Zoom, and Thunderbird on Windows operating systems. Attackers may attempt to masquerade as legitimate processes or exploit vulnerabilities in these applications to execute malicious code. The rule monitors for the creation of child processes by these communication apps and checks if those child processes are unexpected, untrusted, or lack a valid code signature. This detection is crucial because successful exploitation can lead to unauthorized access, data exfiltration, or further compromise of the system. The rule has been actively maintained since August 2023, with updates as recent as May 2026, indicating its relevance and ongoing refinement to address emerging threats.

Attack Chain

User launches a communication application (e.g., Slack, Teams, Webex).
The communication application executes a vulnerable or compromised component.
The compromised component spawns a child process (e.g., powershell.exe, cmd.exe).
The child process executes a malicious command or script.
The script attempts to download additional payloads from an external source.
The payload executes, establishing persistence through registry modification or scheduled tasks.
The attacker gains remote access to the system.
Data exfiltration or lateral movement within the network occurs.

Impact

A successful attack can lead to the compromise of sensitive data, installation of malware, and potential lateral movement within the organization’s network. By exploiting communication applications, attackers can gain access to internal communications, confidential documents, and user credentials. The number of affected users and the extent of the damage depend on the compromised application and the attacker’s objectives. If successful, this attack may lead to significant financial loss, reputational damage, and disruption of business operations.

Recommendation

Deploy the Sigma rule Suspicious Communication App Child Process to your SIEM to detect anomalous child processes spawned by communication applications and tune for your environment.
Enable process creation logging with command line arguments in Windows to ensure that the Sigma rule has the necessary data to function correctly (logsource: process_creation, product: windows).
Investigate any alerts generated by the rule and review the command line arguments of the spawned processes to identify potential malicious activity.
Implement application whitelisting to restrict the execution of unauthorized applications and reduce the attack surface.
Ensure that all communication applications are updated to the latest versions to patch known vulnerabilities and reduce the risk of exploitation.
Examine the network activity of the affected system to identify any suspicious outbound connections that may indicate data exfiltration or communication with a command and control server, referencing the setup guide.

RMM Domain DNS Queries from Non-Browser Processes

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

This detection identifies potentially malicious use of Remote Monitoring and Management (RMM) tools by detecting DNS queries to known RMM domains originating from processes that are not web browsers. Attackers frequently abuse legitimate RMM software for command and control, persistence, and lateral movement within compromised networks. This rule focuses on surfacing RMM clients, scripts, or other non-browser activity contacting these services, thereby increasing the likelihood of detecting unauthorized remote access or malicious activity. The rule aims to reduce false positives by excluding common browser processes and focusing on unusual network activity. The identified domains are associated with various RMM tools like TeamViewer, AnyDesk, and ScreenConnect. This detection is relevant for organizations concerned about insider threats, supply chain attacks, or general compromise leading to unauthorized remote access.

Attack Chain

An attacker gains initial access to a system, possibly through phishing or exploiting a vulnerability.
The attacker installs an unauthorized RMM tool (e.g., using a script or installer).
The RMM tool initiates a DNS query to resolve its command and control domain (e.g., teamviewer.com).
The system, now running the RMM agent, establishes a connection to the attacker-controlled RMM server.
The attacker uses the RMM tool to execute commands on the compromised system.
The attacker uses the RMM tool for lateral movement within the network.
The attacker uses the RMM tool to maintain persistence on the compromised system.

Impact

Compromise via unauthorized RMM tools can provide attackers with persistent remote access, enabling them to perform a range of malicious activities, including data theft, ransomware deployment, and further lateral movement within the network. Successful exploitation can lead to significant financial loss, reputational damage, and disruption of business operations. The number of affected systems can vary depending on the scope of the initial compromise and the attacker’s ability to move laterally.

Recommendation

Deploy the Sigma rule RMM Domain DNS Queries from Non-Browser Processes to your SIEM and tune it to your environment, excluding legitimate non-browser processes that use RMM tools.
Investigate any alerts generated by the rule, focusing on identifying the process making the DNS query and its parent process, as outlined in the rule’s description.
Monitor DNS query logs for queries to the RMM domains listed in the IOC table, and block them at the DNS resolver if unauthorized RMM use is confirmed.
Enable Sysmon Event ID 22 (DNS Query) logging to provide the necessary data for this detection, as recommended in the “Setup” section of the content.

Masquerading Business Application Installers

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

Attackers often attempt to trick users into downloading and executing malicious executables by disguising them as legitimate business applications. This tactic is used to bypass security measures and gain initial access to a system. These malicious executables, often distributed via malicious ads, forum posts, and tutorials, mimic the names of commonly used applications such as Slack, WebEx, Teams, Discord, and Zoom. The executables are typically unsigned or signed with invalid certificates to further evade detection. This allows the attacker to execute arbitrary code on the victim’s machine, potentially leading to further compromise. This campaign aims to target end-users who are less security-aware, and this makes social engineering attacks like this very effective.

Attack Chain

The user visits a compromised website or clicks on a malicious advertisement.
The user is prompted to download an installer file masquerading as a legitimate business application (e.g., Slack, Zoom, Teams) from a download directory.
The downloaded executable is placed in the user’s Downloads folder (e.g., C:\Users*\Downloads*).
The user executes the downloaded file.
The executable, lacking a valid code signature, begins execution.
The malicious installer may drop and execute additional malware components.
The malware establishes persistence, potentially using techniques such as registry key modification.
The malware performs malicious activities, such as data exfiltration or lateral movement.

Impact

Successful execution of a masqueraded business application installer can lead to a complete system compromise. The attacker gains initial access and can deploy various malware payloads, including ransomware, keyloggers, and data stealers. This can result in data breaches, financial loss, and reputational damage. Although the specific number of victims and sectors targeted are not detailed, the widespread use of the applications being spoofed (Slack, Zoom, etc.) suggests a broad potential impact.

Recommendation

Implement the Sigma rule Potential Masquerading as Business App Installer to detect unsigned executables resembling legitimate business applications in download directories.
Enable process creation logging to capture the execution of unsigned executables.
Educate users on the risks of downloading and executing files from untrusted sources.
Implement application whitelisting to restrict the execution of unauthorized applications.
Regularly update endpoint detection and response (EDR) tools to detect and prevent the execution of known malware.
Monitor process execution events for processes originating from the Downloads folder that lack valid code signatures.