Potential Command and Control via Internet Explorer COM Abuse

hello@craftedsignal.io — Wed, 03 Jan 2024 18:12:00 +0000

This detection rule identifies potential command and control (C2) activity abusing Internet Explorer (iexplore.exe) via the Component Object Model (COM) on Windows systems. The technique involves launching iexplore.exe through COM, often using system binaries like rundll32.exe or regsvr32.exe to proxy the execution and evade security controls. The rule focuses on identifying unusual DNS queries originating from iexplore.exe, excluding those directed towards common Microsoft and OCSP-related domains. This tactic allows adversaries to make network connections appearing benign while hosting malicious content or performing C2 functions. The rule is designed for environments using Elastic Defend. The rule was last updated on 2026/05/04.

Attack Chain

Adversary gains initial access to the targeted system (e.g., through phishing or exploiting a vulnerability).
The adversary uses rundll32.exe or regsvr32.exe to load IEProxy.dll, which is used to instantiate Internet Explorer via COM.
Iexplore.exe is launched as a child process of rundll32.exe or regsvr32.exe with the -Embedding flag, indicating it was started via COM.
Iexplore.exe initiates DNS queries to resolve domains for command and control communication or to retrieve malicious payloads.
The DNS queries bypass typical whitelists by using uncommon or attacker-controlled domains.
Iexplore.exe establishes network connections to external IP addresses associated with the malicious domains.
Data is exfiltrated or further commands are received through the established connections.
The adversary maintains persistence and control over the compromised system.

Impact

Successful exploitation allows adversaries to establish a covert command and control channel, potentially leading to data theft, system compromise, or further propagation within the network. The use of Internet Explorer, a trusted system binary, helps evade detection and bypass host-based firewalls. The impact can range from individual workstation compromise to broader network breaches, depending on the attacker’s objectives.

Recommendation

Deploy the Sigma rule Potential Command and Control via Internet Explorer to your SIEM and tune for your environment.
Investigate any alerts generated by the Sigma rule, focusing on the parent processes (rundll32.exe, regsvr32.exe) and the destination domains of the DNS queries.
Monitor process execution events for instances of iexplore.exe being launched with the -Embedding flag, especially when the parent process is rundll32.exe or regsvr32.exe.
Review network connection logs for iexplore.exe to identify any unusual or suspicious outbound connections to domains not associated with standard Microsoft services or internal resources.
Implement network-level controls to block communication with any identified malicious domains.

UAC Bypass Attempt via Elevated COM Internet Explorer Add-On Installer

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

This detection rule identifies a User Account Control (UAC) bypass technique that abuses the Internet Explorer Add-On Installer (ieinstal.exe) to launch malicious programs with elevated privileges. Attackers exploit elevated COM interfaces to circumvent UAC, allowing for stealthy code execution. The specific behavior involves executing a program from a temporary directory using ieinstal.exe with the -Embedding argument. This bypass can be utilized to perform various malicious activities, including installing malware, modifying system settings, or establishing persistence. The targeted systems are Windows endpoints where UAC is enabled. This technique matters because it allows attackers to gain unauthorized access with elevated permissions, undermining standard Windows security controls.

Attack Chain

The attacker gains initial access to the system, possibly through phishing or other means.
The attacker drops a malicious executable into a temporary directory, such as C:\Users\\AppData\Local\Temp\IDC*.tmp\.
The attacker invokes ieinstal.exe with the -Embedding argument, specifying the path to the malicious executable.
ieinstal.exe, running with elevated privileges, launches the malicious executable due to COM object handling.
The malicious executable executes with elevated privileges, bypassing UAC prompts.
The attacker leverages elevated privileges to perform malicious activities, such as installing malware or modifying system settings.
The attacker establishes persistence to maintain elevated access across system reboots.

Impact

Successful exploitation of this UAC bypass technique allows attackers to execute arbitrary code with elevated privileges, bypassing security controls designed to prevent unauthorized system modifications. This can lead to the installation of malware, data theft, or complete system compromise. The severity of the impact is high, as it grants attackers significant control over the affected system.

Recommendation

Deploy the Sigma rule “UAC Bypass Attempt via Elevated COM Internet Explorer Add-On Installer” to your SIEM to detect potential UAC bypass attempts.
Enable Sysmon process creation logging to capture the necessary events for the Sigma rule to function correctly.
Monitor process execution from temporary directories, specifically those matching the pattern C:\\*\\AppData\\*\\Temp\\IDC*.tmp\\*.exe.
Investigate any instances of ieinstal.exe being executed with the -Embedding argument, as this is a key indicator of the UAC bypass attempt.
Implement application whitelisting to prevent unauthorized executables from running, particularly those in temporary directories.

Com — CraftedSignal Threat Feed

Potential Command and Control via Internet Explorer COM Abuse

Attack Chain

Impact

Recommendation

UAC Bypass Attempt via Elevated COM Internet Explorer Add-On Installer

Attack Chain

Impact

Recommendation