https://feed.craftedsignal.io/tags/regasm/Trending threats, MITRE ATT&CK coverage, and detection metadata. Fed continuously.Hugoenhello@craftedsignal.iohello@craftedsignal.ioTue, 09 Jan 2024 12:00:00 +0000https://feed.craftedsignal.io/briefs/2024-01-09-regasm-no-args/Tue, 09 Jan 2024 12:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2024-01-09-regasm-no-args/The execution of regasm.exe without command-line arguments is often indicative of process injection and potential code execution, which could lead to privilege escalation, persistence, or data compromise.The detection analytic identifies instances where regasm.exe is executed without command-line arguments. This behavior is suspicious because RegAsm (Assembly Registration Tool) typically requires arguments specifying which assemblies to register or unregister. The absence of command-line arguments often indicates that the process has been injected into by another process, and its normal execution flow has been altered to evade standard defenses. The detection focuses on endpoint telemetry related to process execution, parent-child relationships, and command-line parameters. It is crucial for defenders because successful exploitation can lead to arbitrary code execution within a trusted process.

Attack Chain

1. An attacker gains initial access to the system through an unspecified method.
2. The attacker injects malicious code into a running process or spawns a new process (e.g., PowerShell).
3. The injected code identifies and targets regasm.exe for process injection.
4. The attacker leverages the process injection technique to execute regasm.exe without command-line arguments.
5. RegAsm, now running without arguments, may execute attacker-controlled code due to the injected malicious payload.
6. The injected code performs malicious actions such as modifying system configurations, creating persistence mechanisms, or escalating privileges.
7. The attacker leverages the compromised process to move laterally within the network and access sensitive data.
8. The final objective could be data exfiltration, system disruption, or deployment of ransomware.

Impact

Successful exploitation can allow attackers to execute arbitrary code within the context of a trusted system process, potentially bypassing application control policies and detection mechanisms. This can lead to privilege escalation, persistence, lateral movement, and data compromise. While the exact number of victims and sectors targeted are unknown, any environment where RegAsm is present is potentially vulnerable, especially developer workstations and servers.

Recommendation

• Deploy the Sigma rules in this brief to your SIEM to detect instances of RegAsm executing without command-line arguments and tune for your environment.
• Enable Sysmon process-creation logging to provide the necessary telemetry for the detection rules.
• Investigate any detected instances of RegAsm executing without arguments to determine the root cause and scope of the compromise.
• Review and harden endpoint security policies to prevent process injection attacks.

]]>highadvisoryregasmprocess-injectiondefense-evasionwindowshttps://feed.craftedsignal.io/briefs/2024-01-regasm-network/Wed, 03 Jan 2024 12:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2024-01-regasm-network/The detection of regasm.exe, a Microsoft-signed binary, establishing a network connection to a public IP address (excluding private ranges) may indicate command and control activity or attempts to bypass application control.The regasm.exe (Assembly Registration Tool) is a legitimate Microsoft-signed binary used for registering .NET assemblies. Adversaries may abuse regasm.exe to bypass application control or establish command and control (C2) communication. This activity is detected by monitoring network connections initiated by regasm.exe to public IP addresses, excluding connections to known private IP ranges. The LOLBAS project has documented the potential misuse of this binary. This activity is significant as it can be used to proxy malicious commands or download payloads. The detection is based on Sysmon Event ID 3 (Network Connect).

Attack Chain

1. The adversary gains initial access through unspecified means (e.g., phishing, exploit).
2. The adversary executes regasm.exe on the compromised system.
3. regasm.exe attempts to establish a network connection to a public IP address.
4. The connection bypasses typical application control restrictions due to the binary being signed by Microsoft.
5. Data is transmitted over the established connection, potentially downloading malicious payloads or sending command execution results.
6. The adversary uses the connection to maintain remote access and control.
7. Further malicious activities are executed, such as lateral movement or data exfiltration.

Impact

A successful attack leveraging regasm.exe for network communication could allow an adversary to establish a persistent command and control channel within the environment. This could lead to further compromise, including data exfiltration, deployment of ransomware, or other malicious activities. The number of victims and targeted sectors are currently unknown.

Recommendation

• Enable Sysmon Event ID 3 (Network Connect) logging to collect the necessary network connection data (Sysmon EventID 3).
• Deploy the Sigma rule "Detect Regasm with Network Connection" to your SIEM and tune for your environment to reduce false positives (Sigma rule).
• Investigate any alerts generated by the "Detect Regasm with Network Connection" rule, focusing on the destination IP address and associated processes (Sigma rule).
• Implement application control policies that monitor and restrict the execution of regasm.exe, even though it's a signed binary, especially when network connections are involved.
• Review endpoint network connection logs for regasm.exe to identify any unusual or suspicious connections to external IP addresses.

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