Adversaries may use ClickOnce applications (.appref-ms and .application files) to proxy execution of code through a trusted Windows utility.(Citation: Burke/CISA ClickOnce BlackHat) ClickOnce is a deployment that enables a user to create self-updating Windows-based .NET applications (i.e, .XBAP, .EXE, or .DLL) that install and run from a file share or web page with minimal user interaction. The application launches as a child process of DFSVC.EXE, which is responsible for installing, launching, and updating the application.(Citation: SpectorOps Medium ClickOnce) Because ClickOnce applications receive only limited permissions, they do not require administrative permissions to install.(Citation: Microsoft Learn ClickOnce) As such, adversaries may abuse ClickOnce to proxy execution of malicious code without needing to escalate privileges. ClickOnce may be abused in a number of ways. For example, an adversary may rely on [User Execution](https://attack.mitre.org/techniques/T1204). When a user visits a malicious website, the .NET malware is disguised as legitimate software and a ClickOnce popup is displayed for installation.(Citation: NetSPI ClickOnce) Adversaries may also abuse ClickOnce to execute malware via a [Rundll32](https://attack.mitre.org/techniques/T1218/011) script using the command `rundll32.exe dfshim.dll,ShOpenVerbApplication1`.(Citation: LOLBAS /Dfsvc.exe) Additionally, an adversary can move the ClickOnce application file to a remote user’s startup folder for continued malicious code deployment (i.e., [Registry Run Keys / Startup Folder](https://attack.mitre.org/techniques/T1547/001)).(Citation: Burke/CISA ClickOnce BlackHat)(Citation: Burke/CISA ClickOnce Paper)
Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries. This involves identifying software or features that are no longer needed or that could be exploited and ensuring they are either removed or properly disabled. This mitigation can be implemented through the following measures: Remove Legacy Software: - Use Case: Disable or remove older versions of software that no longer receive updates or security patches (e.g., legacy Java, Adobe Flash). - Implementation: A company removes Flash Player from all employee systems after it has reached its end-of-life date. Disable Unused Features: - Use Case: Turn off unnecessary operating system features like SMBv1, Telnet, or RDP if they are not required. - Implementation: Disable SMBv1 in a Windows environment to mitigate vulnerabilities like EternalBlue. Control Applications Installed by Users: - Use Case: Prevent users from installing unauthorized software via group policies or other management tools. - Implementation: Block user installations of unauthorized file-sharing applications (e.g., BitTorrent clients) in an enterprise environment. Remove Unnecessary Services: - Use Case: Identify and disable unnecessary default services running on endpoints, servers, or network devices. - Implementation: Disable unused administrative shares (e.g., C$, ADMIN$) on workstations. Restrict Add-ons and Plugins: - Use Case: Remove or disable browser plugins and add-ons that are not needed for business purposes. - Implementation: Disable Java and ActiveX plugins in web browsers to prevent drive-by attacks.
M1021Restrict Web-Based ContentRestricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures: Deploy Web Proxy Filtering: - Use solutions to filter web traffic based on categories, reputation, and content types. - Enforce policies that block unsafe websites or file types at the gateway level. Enable DNS-Based Filtering: - Implement tools to restrict access to domains associated with malware or phishing campaigns. - Use public DNS filtering services to enhance protection. Enforce Content Security Policies (CSP): - Configure CSP headers on internal and external web applications to restrict script execution, iframe embedding, and cross-origin requests. Control Browser Features: - Disable unapproved browser features like automatic downloads, developer tools, or unsafe scripting. - Enforce policies through tools like Group Policy Management to control browser settings. Monitor and Alert on Web-Based Threats: - Use SIEM tools to collect and analyze web proxy logs for signs of anomalous or malicious activity. - Configure alerts for access attempts to blocked domains or repeated file download failures.
M1045Code SigningCode Signing is a security process that ensures the authenticity and integrity of software by digitally signing executables, scripts, and other code artifacts. It prevents untrusted or malicious code from executing by verifying the digital signatures against trusted sources. Code signing protects against tampering, impersonation, and distribution of unauthorized or malicious software, forming a critical defense against supply chain and software exploitation attacks. This mitigation can be implemented through the following measures: Enforce Signed Code Execution: - Implementation: Configure operating systems (e.g., Windows with AppLocker or Linux with Secure Boot) to allow only signed code to execute. - Use Case: Prevent the execution of malicious PowerShell scripts by requiring all scripts to be signed with a trusted certificate. Vendor-Signed Driver Enforcement: - Implementation: Enable kernel-mode code signing to ensure that only drivers signed by trusted vendors can be loaded. - Use Case: A malicious driver attempting to modify system memory fails to load because it lacks a valid signature. Certificate Revocation Management: - Implementation: Use Online Certificate Status Protocol (OCSP) or Certificate Revocation Lists (CRLs) to block certificates associated with compromised or deprecated code. - Use Case: A compromised certificate used to sign a malicious update is revoked, preventing further execution of the software. Third-Party Software Verification: - Implementation: Require software from external vendors to be signed with valid certificates before deployment. - Use Case: An organization only deploys signed and verified third-party software to prevent supply chain attacks. Script Integrity in CI/CD Pipelines: - Implementation: Integrate code signing into CI/CD pipelines to sign and verify code artifacts before production release. - Use Case: A software company ensures that all production builds are signed, preventing tampered builds from reaching customers. **Key Components of Code Signing** - Digital Signature Verification: Verifies the authenticity of code by ensuring it was signed by a trusted entity. - Certificate Management: Uses Public Key Infrastructure (PKI) to manage signing certificates and revocation lists. - Enforced Policy for Unsigned Code: Prevents the execution of unsigned or untrusted binaries and scripts. - Hash Integrity Check: Confirms that code has not been altered since signing by comparing cryptographic hashes.
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