Verclsid

Detection Strategy for T1218.012 Verclsid Abuse

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.

Filter Network Traffic: Employ network appliances and endpoint software to filter ingress, egress, and lateral network traffic. This includes protocol-based filtering, enforcing firewall rules, and blocking or restricting traffic based on predefined conditions to limit adversary movement and data exfiltration. This mitigation can be implemented through the following measures:

Ingress Traffic Filtering:

• Use Case: Configure network firewalls to allow traffic only from authorized IP addresses to public-facing servers.
• Implementation: Limit SSH (port 22) and RDP (port 3389) traffic to specific IP ranges.

Egress Traffic Filtering:

• Use Case: Use firewalls or endpoint security software to block unauthorized outbound traffic to prevent data exfiltration and command-and-control (C2) communications.
• Implementation: Block outbound traffic to known malicious IPs or regions where communication is unexpected.

Protocol-Based Filtering:

• Use Case: Restrict the use of specific protocols that are commonly abused by adversaries, such as SMB, RPC, or Telnet, based on business needs.
• Implementation: Disable SMBv1 on endpoints to prevent exploits like EternalBlue.

Network Segmentation:

• Use Case: Create network segments for critical systems and restrict communication between segments unless explicitly authorized.
• Implementation: Implement VLANs to isolate IoT devices or guest networks from core business systems.

Application Layer Filtering:

• Use Case: Use proxy servers or Web Application Firewalls (WAFs) to inspect and block malicious HTTP/S traffic.
• Implementation: Configure a WAF to block SQL injection attempts or other web application exploitation techniques.

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.