PowerShell

Abuse of PowerShell for Arbitrary Execution

Disable or Remove Feature or Program: 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.

Antivirus/Antimalware: Antivirus/Antimalware solutions utilize signatures, heuristics, and behavioral analysis to detect, block, and remediate malicious software, including viruses, trojans, ransomware, and spyware. These solutions continuously monitor endpoints and systems for known malicious patterns and suspicious behaviors that indicate compromise. Antivirus/Antimalware software should be deployed across all devices, with automated updates to ensure protection against the latest threats. This mitigation can be implemented through the following measures:

Signature-Based Detection:

• Implementation: Use predefined signatures to identify known malware based on unique patterns such as file hashes, byte sequences, or command-line arguments. This method is effective against known threats.
• Use Case: When malware like "Emotet" is detected, its signature (such as a specific file hash) matches a known database of malicious software, triggering an alert and allowing immediate quarantine of the infected file.

Heuristic-Based Detection:

• Implementation: Deploy heuristic algorithms that analyze behavior and characteristics of files and processes to identify potential malware, even if it doesn’t match a known signature.
• Use Case: If a program attempts to modify multiple critical system files or initiate suspicious network communications, heuristic analysis may flag it as potentially malicious, even if no specific malware signature is available.

Behavioral Detection (Behavior Prevention):

• Implementation: Use behavioral analysis to detect patterns of abnormal activities, such as unusual system calls, unauthorized file encryption, or attempts to escalate privileges.
• Use Case: Behavioral analysis can detect ransomware attacks early by identifying behavior like mass file encryption, even before a specific ransomware signature has been identified.

Real-Time Scanning:

• Implementation: Enable real-time scanning to automatically inspect files and network traffic for signs of malware as they are accessed, downloaded, or executed.
• Use Case: When a user downloads an email attachment, the antivirus solution scans the file in real-time, checking it against both signatures and heuristics to detect any malicious content before it can be opened.

Cloud-Assisted Threat Intelligence:

• Implementation: Use cloud-based threat intelligence to ensure the antivirus solution can access the latest malware definitions and real-time threat feeds from a global database of emerging threats.
• Use Case: Cloud-assisted antivirus solutions quickly identify newly discovered malware by cross-referencing against global threat databases, providing real-time protection against zero-day attacks.

Tools for Implementation:

• Endpoint Security Platforms: Use solutions such as EDR for comprehensive antivirus/antimalware protection across all systems.
• Centralized Management: Implement centralized antivirus management consoles that provide visibility into threat activity, enable policy enforcement, and automate updates.
• Behavioral Analysis Tools: Leverage solutions with advanced behavioral analysis capabilities to detect malicious activity patterns that don’t rely on known signatures.

Code Signing: Code 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.

Privileged Account Management: Privileged Account Management focuses on implementing policies, controls, and tools to securely manage privileged accounts (e.g., SYSTEM, root, or administrative accounts). This includes restricting access, limiting the scope of permissions, monitoring privileged account usage, and ensuring accountability through logging and auditing.This mitigation can be implemented through the following measures:

Account Permissions and Roles:

• Implement RBAC and least privilege principles to allocate permissions securely.
• Use tools like Active Directory Group Policies to enforce access restrictions.

Credential Security:

• Deploy password vaulting tools like CyberArk, HashiCorp Vault, or KeePass for secure storage and rotation of credentials.
• Enforce password policies for complexity, uniqueness, and expiration using tools like Microsoft Group Policy Objects (GPO).

Multi-Factor Authentication (MFA):

• Enforce MFA for all privileged accounts using Duo Security, Okta, or Microsoft Azure AD MFA.

Privileged Access Management (PAM):

• Use PAM solutions like CyberArk, BeyondTrust, or Thycotic to manage, monitor, and audit privileged access.

Auditing and Monitoring:

• Integrate activity monitoring into your SIEM (e.g., Splunk or QRadar) to detect and alert on anomalous privileged account usage.

Just-In-Time Access:

• Deploy JIT solutions like Azure Privileged Identity Management (PIM) or configure ephemeral roles in AWS and GCP to grant time-limited elevated permissions.

Tools for Implementation

Privileged Access Management (PAM):

• CyberArk, BeyondTrust, Thycotic, HashiCorp Vault.

Credential Management:

• Microsoft LAPS (Local Admin Password Solution), Password Safe, HashiCorp Vault, KeePass.

Multi-Factor Authentication:

• Duo Security, Okta, Microsoft Azure MFA, Google Authenticator.

Linux Privilege Management:

• sudo configuration, SELinux, AppArmor.

Just-In-Time Access:

• Azure Privileged Identity Management (PIM), AWS IAM Roles with session constraints, GCP Identity-Aware Proxy.

Execution Prevention: Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms. This ensures that only trusted and authorized code is executed, reducing the risk of malware and unauthorized actions. This mitigation can be implemented through the following measures:

Application Control:

• Use Case: Use tools like AppLocker or Windows Defender Application Control (WDAC) to create whitelists of authorized applications and block unauthorized ones. On Linux, use tools like SELinux or AppArmor to define mandatory access control policies for application execution.
• Implementation: Allow only digitally signed or pre-approved applications to execute on servers and endpoints. (e.g., New-AppLockerPolicy -PolicyType Enforced -FilePath "C:\Policies\AppLocker.xml")

Script Blocking:

• Use Case: Use script control mechanisms to block unauthorized execution of scripts, such as PowerShell or JavaScript. Web Browsers: Use browser extensions or settings to block JavaScript execution from untrusted sources.
• Implementation: Configure PowerShell to enforce Constrained Language Mode for non-administrator users. (e.g., Set-ExecutionPolicy AllSigned)

Executable Blocking:

• Use Case: Prevent execution of binaries from suspicious locations, such as %TEMP% or %APPDATA% directories.
• Implementation: Block execution of .exe, .bat, or .ps1 files from user-writable directories.

Dynamic Analysis Prevention:

• Use Case: Use behavior-based execution prevention tools to identify and block malicious activity in real time.
• Implemenation: Employ EDR solutions that analyze runtime behavior and block suspicious code execution.