Indicator Removal: Clear Network Connection History and Configurations
Other sub-techniques of Indicator Removal (10)
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):
* HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Default
* HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Servers
Windows may also store information about recent RDP connections in files such as C:\Users\\%username%\Documents\Default.rdp
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.
Procedure Examples |
|
Name | Description |
---|---|
SUNBURST |
SUNBURST also removed the firewall rules it created during execution.(Citation: Microsoft Deep Dive Solorigate January 2021) |
Volt Typhoon |
Volt Typhoon has inspected server logs to remove their IPs.(Citation: Secureworks BRONZE SILHOUETTE May 2023) |
Mitigations |
|
Mitigation | Description |
---|---|
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 |
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. |
References
- Sarah Edwards. (2020, April 30). Analysis of Apple Unified Logs: Quarantine Edition [Entry 6] – Working From Home? Remote Logins. Retrieved August 19, 2021.
- rjben. (2012, May 30). How do you find the culprit when unauthorized access to a computer is a problem?. Retrieved August 3, 2022.
- Moran, B. (2020, November 18). Putting Together the RDPieces. Retrieved October 17, 2022.
- Microsoft. (2021, September 24). How to remove entries from the Remote Desktop Connection Computer box. Retrieved June 15, 2022.
- freedesktop.org. (n.d.). systemd-journald.service. Retrieved June 15, 2022.
- MSTIC, CDOC, 365 Defender Research Team. (2021, January 20). Deep dive into the Solorigate second-stage activation: From SUNBURST to TEARDROP and Raindrop . Retrieved January 22, 2021.
- Counter Threat Unit Research Team. (2023, May 24). Chinese Cyberespionage Group BRONZE SILHOUETTE Targets U.S. Government and Defense Organizations. Retrieved July 27, 2023.
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