Adversaries may clear artifacts associated with previously established persistence on a host system to remove evidence of their activity. This may involve various actions, such as removing services, deleting executables, Modify Registry, Plist File Modification, or other methods of cleanup to prevent defenders from collecting evidence of their persistent presence.(Citation: Cylance Dust Storm) Adversaries may also delete accounts previously created to maintain persistence (i.e. Create Account).(Citation: Talos - Cisco Attack 2022) In some instances, artifacts of persistence may also be removed once an adversary’s persistence is executed in order to prevent errors with the new instance of the malware.(Citation: NCC Group Team9 June 2020)
Detects adversary activity that removes persistence artifacts such as services, registry keys, scheduled tasks, user accounts, and binaries through commands like `sc delete`, `schtasks /delete`, or `reg delete`.
Detects deletion of launch agents (~/Library/LaunchAgents/) and launch daemons (/Library/LaunchDaemons/), especially after suspicious process execution or when tied to known persistence methods.
Detects removal of persistence artifacts such as crontab entries, systemd service units, and malicious user accounts through commands like `crontab -r`, `rm /etc/systemd/system/*.service`, or `userdel`.
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`.
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.