Adversaries may clear or remove evidence of malicious network connections in order to clean up traces of their operations. Configuration settings as well as various artifacts that highlight connection history may be created on a system and/or in application logs from behaviors that require network connections, such as Remote Services or External Remote Services. Defenders may use these artifacts to monitor or otherwise analyze network connections created by adversaries. Network connection history may be stored in various locations. For example, RDP connection history may be stored in Windows Registry values under (Citation: Microsoft RDP Removal): * <code>HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default</code> * <code>HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers</code> Windows may also store information about recent RDP connections in files such as <code>C:\Users\\%username%\Documents\Default.rdp</code> and `C:\Users\%username%\AppData\Local\Microsoft\Terminal Server Client\Cache\`.(Citation: Moran RDPieces) Similarly, macOS and Linux hosts may store information highlighting connection history in system logs (such as those stored in `/Library/Logs` and/or `/var/log/`).(Citation: Apple Culprit Access)(Citation: FreeDesktop Journal)(Citation: Apple Unified Log Analysis Remote Login and Screen Sharing) Malicious network connections may also require changes to third-party applications or network configuration settings, such as Disable or Modify System Firewall or tampering to enable Proxy. Adversaries may delete or modify this data to conceal indicators and/or impede defensive analysis.
Detects deletion or overwriting of logs/configs that store SSH or proxy activity, such as /var/log/auth.log or custom .bash_history clearing tied to SSH sessions or firewall rule changes.
Detects firewall rule modifications or reset of logs/connection tables (e.g., `clear logging`, `erase startup-config`, `write erase`) following remote access activity on routers, switches, or VPN appliances.
Detects removal of Remote Login or Screen Sharing logs in Unified Logging, deletion of `com.apple.UTun`, or suspicious Terminal use of `rm`, `sudo pfctl -F all` to clear network state/config history.
Restrict Registry Permissions
Restricting registry permissions involves configuring access control settings for sensitive registry keys and hives to ensure that only authorized users or processes can make modifications. By limiting access, organizations can prevent unauthorized changes that adversaries might use for persistence, privilege escalation, or defense evasion. This mitigation can be implemented through the following measures: Review and Adjust Permissions on Critical Keys - Regularly review permissions on keys such as `Run`, `RunOnce`, and `Services` to ensure only authorized users have write access. - Use tools like `icacls` or `PowerShell` to automate permission adjustments. Enable Registry Auditing - Enable auditing on sensitive keys to log access attempts. - Use Event Viewer or SIEM solutions to analyze logs and detect suspicious activity. - Example Audit Policy: `auditpol /set /subcategory:"Registry" /success:enable /failure:enable` Protect Credential-Related Hives - Limit access to hives like `SAM`,`SECURITY`, and `SYSTEM` to prevent credential dumping or other unauthorized access. - Use LSA Protection to add an additional security layer for credential storage. Restrict Registry Editor Usage - Use Group Policy to restrict access to regedit.exe for non-administrative users. - Block execution of registry editing tools on endpoints where they are unnecessary. Deploy Baseline Configuration Tools - Use tools like Microsoft Security Compliance Toolkit or CIS Benchmarks to apply and maintain secure registry configurations. *Tools for Implementation* Registry Permission Tools: - Registry Editor (regedit): Built-in tool to manage registry permissions. - PowerShell: Automate permissions and manage keys. `Set-ItemProperty -Path "HKLM:\Software\Microsoft\Windows\CurrentVersion\Run" -Name "KeyName" -Value "Value"` - icacls: Command-line tool to modify ACLs. Monitoring Tools: - Sysmon: Monitor and log registry events. - Event Viewer: View registry access logs. Policy Management Tools: - Group Policy Management Console (GPMC): Enforce registry permissions via GPOs. - Microsoft Endpoint Manager: Deploy configuration baselines for registry permissions.
Remote Data Storage
Remote Data Storage focuses on moving critical data, such as security logs and sensitive files, to secure, off-host locations to minimize unauthorized access, tampering, or destruction by adversaries. By leveraging remote storage solutions, organizations enhance the protection of forensic evidence, sensitive information, and monitoring data. This mitigation can be implemented through the following measures: Centralized Log Management: - Configure endpoints to forward security logs to a centralized log collector or SIEM. - Use tools like Splunk Graylog, or Security Onion to aggregate and store logs. - Example command (Linux): `sudo auditd | tee /var/log/audit/audit.log | nc <remote-log-server> 514` Remote File Storage Solutions: - Utilize cloud storage solutions like AWS S3, Google Cloud Storage, or Azure Blob Storage for sensitive data. - Ensure proper encryption at rest and access control policies (IAM roles, ACLs). Intrusion Detection Log Forwarding: - Forward logs from IDS/IPS systems (e.g., Zeek/Suricata) to a remote security information system. - Example for Suricata log forwarding: `outputs: - type: syslog protocol: tls address: <remote-syslog-server>` Immutable Backup Configurations: - Enable immutable storage settings for backups to prevent adversaries from modifying or deleting data. - Example: AWS S3 Object Lock. Data Encryption: - Ensure encryption for sensitive data using AES-256 at rest and TLS 1.2+ for data in transit. Tools: OpenSSL, BitLocker, LUKS for Linux.