Path Interception by PATH Environment Variable

Detection Strategy for Hijack Execution Flow using Path Interception by PATH Environment Variable.

Restrict File and Directory Permissions: Restricting file and directory permissions involves setting access controls at the file system level to limit which users, groups, or processes can read, write, or execute files. By configuring permissions appropriately, organizations can reduce the attack surface for adversaries seeking to access sensitive data, plant malicious code, or tamper with system files.

Enforce Least Privilege Permissions:

• Remove unnecessary write permissions on sensitive files and directories.
• Use file ownership and groups to control access for specific roles.

Example (Windows): Right-click the shared folder → Properties → Security tab → Adjust permissions for NTFS ACLs.

Harden File Shares:

• Disable anonymous access to shared folders.
• Enforce NTFS permissions for shared folders on Windows.

Example: Set permissions to restrict write access to critical files, such as system executables (e.g., /bin or /sbin on Linux). Use tools like chown and chmod to assign file ownership and limit access.

On Linux, apply: chmod 750 /etc/sensitive.conf chown root:admin /etc/sensitive.conf

File Integrity Monitoring (FIM):

• Use tools like Tripwire, Wazuh, or OSSEC to monitor changes to critical file permissions.

Audit File System Access:

• Enable auditing to track permission changes or unauthorized access attempts.
• Use auditd (Linux) or Event Viewer (Windows) to log activities.

Restrict Startup Directories:

• Configure permissions to prevent unauthorized writes to directories like C:\ProgramData\Microsoft\Windows\Start Menu.

Example: Restrict write access to critical directories like /etc/, /usr/local/, and Windows directories such as C:\Windows\System32.

• On Windows, use icacls to modify permissions: icacls "C:\Windows\System32" /inheritance:r /grant:r SYSTEM:(OI)(CI)F
• On Linux, monitor permissions using tools like lsattr or auditd.

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.

Audit: Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations. The primary purpose of auditing is to detect anomalies and identify potential threats or weaknesses in the environment. Proper auditing configurations can also help to meet compliance requirements. The process of auditing encompasses regular analysis of user behaviors and system logs in support of proactive security measures.

Auditing is applicable to all systems used within an organization, from the front door of a building to accessing a file on a fileserver. It is considered more critical for regulated industries such as, healthcare, finance and government where compliance requirements demand stringent tracking of user and system activates.This mitigation can be implemented through the following measures:

System Audit:

• Use Case: Regularly assess system configurations to ensure compliance with organizational security policies.
• Implementation: Use tools to scan for deviations from established benchmarks.

Permission Audits:

• Use Case: Review file and folder permissions to minimize the risk of unauthorized access or privilege escalation.
• Implementation: Run access reviews to identify users or groups with excessive permissions.

Software Audits:

• Use Case: Identify outdated, unsupported, or insecure software that could serve as an attack vector.
• Implementation: Use inventory and vulnerability scanning tools to detect outdated versions and recommend secure alternatives.

Configuration Audits:

• Use Case: Evaluate system and network configurations to ensure secure settings (e.g., disabled SMBv1, enabled MFA).
• Implementation: Implement automated configuration scanning tools like SCAP (Security Content Automation Protocol) to identify non-compliant systems.

Network Audits:

• Use Case: Examine network traffic, firewall rules, and endpoint communications to identify unauthorized or insecure connections.
• Implementation: Utilize tools such as Wireshark, or Zeek to monitor and log suspicious network behavior.