Slack — CraftedSignal Threat Feed

Detection of Command and Control Activity via Commonly Abused Web Services

hello@craftedsignal.io — Thu, 04 Jan 2024 12:00:00 +0000

Adversaries may implement command and control (C2) communications that use common web services to hide their activity. This attack technique is typically targeted at an organization and uses web services common to the victim network, which allows the adversary to blend into legitimate traffic activity. These popular services are typically targeted since they have most likely been used before compromise, which helps malicious traffic blend in. This detection focuses on identifying connections from Windows hosts to a predefined list of commonly abused web services from processes running outside of typical program installation directories, indicating a potential C2 channel leveraging legitimate services. The rule aims to detect this behavior by monitoring network connections and DNS requests originating from unusual locations.

Attack Chain

Initial access is achieved via an unknown method (e.g., phishing, exploit).
Malware is installed on the victim’s system, likely outside typical program directories.
The malware establishes a DNS connection to a commonly abused web service (e.g., pastebin.com, raw.githubusercontent.com) to obscure C2 traffic.
The malware sends encrypted or encoded commands to the web service.
The web service acts as an intermediary, relaying the commands to the attacker’s C2 server.
The C2 server responds with instructions, which are then relayed back to the compromised host through the same web service.
The malware executes the received commands, potentially leading to data exfiltration, lateral movement, or other malicious activities.
The attacker maintains persistent access and control over the compromised system using the web service as a hidden C2 channel.

Impact

Successful exploitation can lead to data theft, system compromise, and further propagation within the network. Since commonly used web services are utilized, the malicious activity can blend in with legitimate network traffic, making it difficult to detect. The impact can range from minor data breaches to complete network compromise, depending on the attacker’s objectives and the level of access gained.

Recommendation

Deploy the Sigma rule Detect Commonly Abused Web Services via DNS to your SIEM to identify suspicious DNS queries to known C2 web services originating from anomalous processes.
Enable DNS query logging on Windows endpoints to provide the data source required for the Sigma rule.
Review network connection logs for processes outside standard installation directories communicating with domains listed in the query section of the Sigma rule to identify potential C2 activity.
Implement network segmentation to limit the potential impact of compromised hosts.

Unusual Process Loading Mozilla NSS/Mozglue Module

hello@craftedsignal.io — Wed, 03 Jan 2024 14:30:00 +0000

This brief focuses on detecting anomalous loading of Mozilla NSS (Network Security Services) and Mozglue libraries (specifically mozglue.dll and nss3.dll) by processes other than known Mozilla applications like Firefox and Thunderbird. The technique leverages Windows Sysmon Event ID 7 (ImageLoaded) to identify such instances. This activity is flagged as suspicious because legitimate software rarely loads these libraries outside of the intended Mozilla ecosystem. Attackers may attempt to load these libraries into other processes to perform malicious actions such as code injection, data exfiltration, or credential theft, while masquerading as legitimate software. This detection is crucial for identifying potentially compromised systems and preventing further damage.

Attack Chain

Initial Access: An attacker gains initial access to the system, possibly through phishing, exploiting a vulnerability, or using stolen credentials.
Persistence: The attacker establishes persistence on the system, ensuring continued access even after a reboot. This may involve creating scheduled tasks or modifying registry keys.
Privilege Escalation: The attacker elevates privileges to gain higher-level access to the system. This can be achieved through exploiting kernel vulnerabilities or misconfigured services.
Malware Installation: The attacker deploys malware or malicious tools onto the compromised system. This may involve downloading executables or scripts from a remote server.
Code Injection: The attacker injects malicious code into a legitimate process. This is often done to evade detection and execute malicious commands in a trusted context. In this scenario, the injected code might leverage Mozilla NSS/Mozglue libraries.
Credential Theft: The injected code attempts to steal credentials stored on the system. This may involve accessing LSASS memory or extracting credentials from web browsers.
Data Exfiltration: The attacker exfiltrates sensitive data from the compromised system. This may involve compressing data and transferring it to a remote server using protocols like HTTP or FTP.
Lateral Movement/Impact: Using stolen credentials or the compromised system as a pivot, the attacker moves laterally within the network to compromise additional systems, or achieves their ultimate objective, such as ransomware deployment or intellectual property theft.

Impact

Successful exploitation and anomalous loading of Mozilla libraries can lead to significant damage, including data breaches, financial loss, and reputational damage. Stolen credentials can be used to access sensitive systems and data, while injected code can disrupt critical business processes. The scope can range from individual workstations to entire networks, depending on the attacker’s objectives and level of access. The detection helps prevent credential theft, data exfiltration, and lateral movement.

Recommendation

Enable Sysmon Event ID 7 (ImageLoaded) logging on all Windows endpoints to ensure visibility into loaded modules (reference: data_source).
Deploy the Sigma rule Unusual Mozilla NSS/Mozglue Module Load by Non-Mozilla Process to your SIEM and tune the process exceptions for your environment (reference: rules).
Investigate any instances where Mozilla NSS/Mozglue libraries are loaded by processes not explicitly allowed in the exception list to determine if malicious activity is occurring (reference: search).
Correlate detections of unusual Mozilla library loading with other suspicious activity, such as network connections to known malicious domains or the execution of unusual processes, to identify potential compromises (reference: tags).
Review and update the list of legitimate applications that may load Mozilla NSS/Mozglue libraries in your environment to reduce false positives (reference: known_false_positives).

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.