Exploitation of Weak File and Directory Permissions

Overview

Exploitation of weak file and directory permissions is a technique where adversaries leverage improperly configured access controls to gain unauthorized access, escalate privileges, or maintain persistence within a system. This method is utilized across multiple stages of the attack lifecycle due to the widespread presence of misconfigured permissions in both on-premises and cloud environments.

Attack Objective

• Gain unauthorized access or elevate privileges by exploiting excessive or misconfigured permissions
• Supports stages including Initial Access, Persistence, Privilege Escalation, and Defense Evasion
• Advances attacker position by enabling access to sensitive files, execution of malicious code, or modification of system configurations

How the Technique Works

Adversaries identify files or directories with permissions that allow unintended read, write, or execute capabilities. By exploiting these weaknesses, attackers can read sensitive data, modify files to implant malicious code, replace executables, or create backdoors. This exploitation often bypasses security controls by leveraging legitimate system functionalities and trusted file paths.

Common Methods & Variations

• Modifying permissions to gain write access to system or application files
• Replacing or injecting malicious code into executables or scripts with weak execute permissions
• Exploiting world-writable directories or files in on-premises servers and cloud storage buckets
• Leveraging identity and access misconfigurations in cloud environments to access or alter files
• Using living-off-the-land binaries (LOLBins) to interact with files and directories without deploying additional tools

Indicators of Compromise (IOCs)

• Unusual file permission changes or access patterns in system and application logs
• Creation or modification of files in sensitive directories by non-privileged accounts
• Execution of binaries or scripts from unexpected locations
• Alerts from file integrity monitoring systems indicating unauthorized changes
• Cloud audit logs showing anomalous access to storage buckets or file shares

Detection Strategies

• Monitoring file system and directory permission changes through endpoint detection and response (EDR) tools
• Behavioral analysis to identify abnormal file access or modification by users or processes
• Correlation of access logs with identity and access management (IAM) events in cloud environments
• File integrity monitoring combined with alerting on deviations from baseline permissions

Mitigation & Prevention

• Implement the principle of least privilege for file and directory permissions
• Regularly audit and remediate overly permissive access controls on critical files and directories
• Enforce strong access policies and segmentation in both on-premises and cloud storage systems
• Use file integrity monitoring and automated alerts for unauthorized permission changes
• Apply identity and access management best practices to restrict access in cloud environments

Response Considerations

• Immediately restrict or revoke excessive permissions identified during investigation
• Conduct a thorough audit of affected files, directories, and access logs to determine scope
• Identify and remove any implanted malicious code or backdoors
• Harden permissions and implement continuous monitoring to prevent recurrence
• Review and update security policies and user training to reduce risk of misconfiguration

Related Techniques

• Privilege Escalation via Access Token Manipulation
• Persistence through Implantation of Malicious Files
• Lateral Movement using Shared Network Resources
• Defense Evasion by Modifying System Binaries or Scripts

Mapping & References

• MITRE ATT&CK Tactics: Initial Access, Persistence, Privilege Escalation, Defense Evasion
• MITRE ATT&CK Techniques: T1055 (Process Injection), T1078 (Valid Accounts), T1548 (Abuse Elevation Control Mechanism)
• Public advisories on file permission misconfigurations in cloud storage (e.g., AWS S3, Azure Blob Storage)
• Industry reports on exploitation of weak permissions in ransomware and advanced persistent threat (APT) campaigns