What are file permissions: exploring their role in system and data protection

File permissions are the equivalent of a “gatekeeper” for data and can allow you toControl which users can view, edit or execute specific files and directories。

By understanding and effectively managing file permissions, you can create multiple layers of security that dramatically reduce the risk of unauthorized access or accidental modification.

This paper will delve into the concept of file permissions, highlighting its importance in data security.

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The role of file permissions in data security

File permissions are critical to maintaining data security and protecting sensitive information.

It is a means of controlling access to files and directories that prevents unauthorized users from modifying or accessing data.

1. Managing access to sensitive data

The central role of file permissions is toControl access to sensitive data-- Enforcing access restrictions to ensure that only authorized individuals or groups have access to classified information by clarifying who can read, write or execute files and directories.

Setting reasonable file permissions is important forProtection against unauthorized access, modification or deletion of dataVital:

• It prevents accidental or intentional misuse of sensitive information and safeguards data integrity;
• Reduce the risk of data breaches and unauthorized disclosures.

2. Prevention of unauthorized modifications

File permissions effectively limit write permissions and protect sensitive data, thus preventing unauthorized changes to files and directories.

However, if permissions are misconfigured or over-opened, it may result in aLoss, corruption and unauthorized alteration of data：

• It could also lead to security breaches, such as allowing unauthorized users to plant malicious code;
• Regularly reviewing and establishing reasonable access controls can circumvent these risks and safeguard data integrity and security.

3. Reducing the risk of data breaches

The correctly configured file permissions are reduceddata leakThe key to risk: it restricts access to sensitive files, ensuring that only authorized users or groups can operate on them.

By setting reasonable permissions, companies can prevent unauthorized users fromTampering with or stealing dataThe information is confidential, and thus the confidentiality and integrity of the information is safeguarded.

This control mechanism directly reduces the risk of data leakage by restricting access to sensitive files (allowing only authorized persons to modify, view or delete them).

4. Ensuring compliance with data privacy legislation

Proper file permissions are a core aspect of an organization's ability to meet data privacy and compliance requirements.

Control access to sensitive data by setting permissions to ensure that only authorized individuals or groups can operate the data, thus reducing the exposure of sensitive information to unauthorized users and safeguarding data privacy.

In addition, document permissions can help organizations to comply with the legal and regulatory framework: manyData privacy laws(e.g. the General Data Protection Regulation (GDPR)) explicitly requires companies to take adequate security measures to protect personal data, and reasonable file permissions are an important part of such measures.

5. Protection of system resources

Setting reasonable file permissions is the key to preventing system vulnerabilities.

If permissions are misconfigured or overly open, security risks arise: unauthorized users can plant malicious code, access sensitive data, or compromise the integrity of the computing environment.

By properly configuring profile permissions, organizations can circumvent these risks and maintain overall system security against potential vulnerabilities.

Managing File Permissions

Effective file rights management is the core of safeguarding data security and controlling access to sensitive files and resources.

It enables organizations to grant only the necessary permissions to authorized users, ensuring that users have reasonable privileges to access, modify or execute files.

Understanding File Permissions

File permissions are used to control the scope of access to files and directories, the core contains three types of permissions: read (r), write (w), implementation (x), the specific meaning of which is as follows:

• Read (r): Allows the user to view the contents of a file, but not to modify or delete it;
• Write (w): Allow users to modify or delete files;
• Implementation (x): Allows the user to run an executable file, or access a directory.

File permissions are represented in two ways: symbolic representation (e.g. “rw-r-r-”) with a numerical representation (e.g., 644):

• Symbolic representation: letters with symbols to represent the owner (u), group (g), other users (o) permissions;
• Numeric representation: Assign numeric values to each permission (Read = 4, Write = 2, Execute = 1) and calculate the total permissions by adding them up.

InUnix-like systemsIn this case, you can use thechmodCommand profile permissions; in the GUI environment, they can be set via the “File Properties” function.

User-based rights management

To manage file permissions for an individual user, follow these steps:

1. task: Usechmodcommand, followed by a username or user ID, grants read (r), write (w), and execute (x) privileges.
   Example:chmod u+rwx 文件名-- Grant full read, write, and execute permissions to the target file for this user.
2. Modify permissions: Also usechmodcommand, paired with the symbol (+ or -) Adjust existing permissions for specific users.
   Example:chmod u-w 文件名-- Revoke this user's write permissions to the target file.
3. Revocation of authority: Similar to modifying permissions, usingchmodThe command is paired with the symbol (–) Revoke a particular privilege for a specific user.
   Example:chmod u-x 文件名-- Revoke this user's execute permissions on the target file.

Note: The appropriate privileges or administrator access are required to perform the above operations.

Group-based rights management

Group-based permissions management refers to the bulk assignment of file permissions to groups of users, rather than to individual users. This approach simplifies the control of permissions for “multiple users with the same access needs”.

To create and manage user groups and assign file permissions to groups, follow the steps below:

1. Create Group: Use the corresponding command (e.g. **)groupadd**) New user group.
   Example:groupadd mygroup(create a user group named “mygroup”).
2. Ownership of allocation groups: Usechowncommand assigns group ownership to a file or directory.
   Example:chown :mygroup 我的文件(Assign group ownership of “my files” to “mygroup”).
3. Setting Group Permissions: Usechmodcommand with the group symbol (g) to assign permissions to a group.
   Example:chmod g+rwx 我的文件(Grant read, write, and execute permissions to the group “mygroup” for “My Files”).
4. Adding Users to Groups: Useusermodcommand to add users to the target group.
   Example:usermod -aG mygroup 用户名(add “username” to the “mygroup” group).
5. Removing a user from a group: Usegpasswdcommand removes the user from the group.
   Example:gpasswd -d 用户名 mygroup(remove “username” from the “mygroup” group).

Setting directory permissions

Setting directory permissions appropriately is critical to maintaining file system security, privacy and access control in the following ways:

1. utilizationchmodcommand to configure permissions through numeric or symbolic representations:
   • numeric representation: Each digit corresponds to the permissions of the owner, group, and other users (e.g.755）；
   • symbolic representation: Use the letters (u= Owner,g= Group,o= Other users,a(= all users) with “+” “-” to specify permissions.
2. Example of numerical representation:
   chmod 755 目录名-- Grants read, write, and execute permissions for the owner (7=4+2+1), and read and execute permissions for the group with other users (5=4+1).
3. Example of symbolic representation:
   chmod u=rwx, g=rx, o=rx 目录名-- The effect of the authority is consistent with the numerical representation above.
4. Special privilege settings:
   • Setuid (set user ID)：chmod u+s 文件-- Allow executables to run with owner's rights;
   • Setgid (Set Group ID)：chmod g+s 目录-- Allows a file or directory to inherit group ownership from a parent directory;
   • Sticky bit：chmod +t 目录-- Allows only the file owner, directory owner, or root user to delete/rename files in a directory.

Advanced Privilege Setting

Access Control Lists（ACLs (Access Control Lists) and Extended Attributes are advanced privilege settings that provide greater flexibility and granularity for file access control.

ACLs allow you to go beyond the traditional “owner, group, other users” framework and define permissions for specific users or groups, enabling granular access control by user/group.

How ACLs are used:

• View ACLs: Usegetfaclcommand (e.g.getfacl 我的文件) View the ACL configuration for a file or directory;
• Modifying ACLs: Usesetfaclcommand (e.g.setfacl -m u:用户名:rwx 我的文件) Grants/withdraws permissions for a specific user or group;
• Deleting ACLs: Usesetfaclorder matching-xOptions (e.g.setfacl -x u:用户名 我的文件) Deletes ACL entries for a specific user or group.

Usage of extended attributes:

Extended attributes are metadata attached to a file or directory that can store custom access control information or define specific file behavior as follows:

• View Extended Properties: Usegetfattrcommand (e.g.getfattr -d 我的文件) to view the extended attributes of a file or directory;
• Setting Extended Properties: Usesetfattrcommand (e.g.setfattr -n user.自定义属性 -v "值" 我的文件) Create or set extended properties;
• Deleting Extended Properties: Usesetfattrorder matching-xOptions (e.g.setfattr -x user.自定义属性 我的文件) Remove specific extension attributes.

Through ACLs and extended attributes, you can customize file access control rules to define specific file behaviors according to actual needs.

Automated Rights Management

Automated privilege management tools are a class of tools thatStreamline and efficiently handle document rights management taskssoftware solutions.

Through automation technology, these tools can automatically perform privilege granting/revoking, privilege setting, compliance checking, etc. without human intervention.

The benefits of automated rights management include increased efficiency, reduced human error, enhanced security, and streamlined auditing and compliance processes.

Audit and monitor file permissions

Auditing and monitoring of file permissions is critical to security and compliance:

• Regular audits identify unauthorized privilege changes, potential security breaches, and ensure compliance with industry regulations;
• The monitoring tool enablesreal time detectionSuspicious behavior (e.g., unauthorized access or privilege modification).

How to perform regular audits and controls:

1. Establish a document authority review schedule (e.g., annually, or immediately after major system changes);
2. Identify key documents and catalogs to focus on;
3. Review the existing permissions on each file / directory to ensure compliance with the Least Privilege Principle;
4. Verify that permissions are consistent with corporate security policies and regulatory requirements;
5. Remove unnecessary or excessive permissions;
6. Use monitoring tools to set up alerts/notifications for unauthorized privilege changes or suspicious behavior.

File Permissions Best Practices

Proper file rights management is key to safeguarding the security and integrity of your system, and the following are recommended best practices:

least authority principle (LAP)

The principle of least privilege is a core security concept: granting users and processes only what is necessary to perform their tasks.least privilege。

File permissions are the key vehicle for implementing this principle -- they determine the level of access users and groups have to files and directories on the system.

How to assign Least Necessary Privileges:

1. Clarify the specific tasks and responsibilities of each user or group;
2. Determine the minimum set of permissions required to perform these tasks;
3. Assign the appropriate privileges based on the principle of least privilege;
4. Use standard permissions to control the scope of access;
5. Permissions are assigned by symbolic/numeric representation;
6. Test the permissions configuration to ensure that only necessary access is granted.

Periodic review and updating of competencies

Regularly reviewing and updating file permissions is key to maintaining system security: as systems evolve, user roles change, and new security threats emerge, old permissions may become outdated or misconfigured.

Guidelines for periodic audits:

1. Establish a privilege review schedule (e.g., annually, or implemented after major system changes);
2. Identify key documents and catalogs that need to be checked periodically;
3. Review the existing permissions for each file/directory;
4. Ensure that permissions conform to the principle of least privilege;
5. Authentication permissions are consistent with corporate security policies and regulatory requirements;
6. Remove unnecessary or excessive permissions.

Implementation of role-based access control (RBAC)

Role-based access control (RBAC) is a security model: access rights and permissions are assigned based on the user's role in the organization.

RBAC simplifies privilege management by categorizing “users with similar responsibilities” into roles and assigning privileges to roles rather than individual users.

This approach provides more efficient and scalable control over access to files and resources.

Advantages of RBAC:

1. Simplified management: Bulk management of permissions through roles reduces the cost of operating permissions for individual users;
2. Delegation of authority by function: Permissions are assigned based on job responsibilities, ensuring that users only have the permissions they need to perform their tasks;
3. scalability: When your organization expands or personnel changes, you can simply add/modify roles without having to adjust user permissions one by one.

How to implement RBAC with file permissions:

1. Identify the different user roles within the organization based on job responsibilities;
2. Determine the specific access rights required for each role;
3. Create user groups corresponding to the roles;
4. Assign permissions to each group based on the principle of least privilege;
5. Add the relevant user to the corresponding group;
6. Ensure that ownership of files and directories is correctly assigned to users and groups.

Simplify rights management with user groups

Managing file permissions through user groups has significant advantages over “assigning permissions to individual users”:

1. Simplified management: No need to manage user permissions one by one, just assign permissions to groups, reducing management costs;
2. scalabilityWhen a user joins/leaves the organization, he/she is simply added/removed to/from the corresponding group, simplifying the process of adjusting privileges;
3. consistency: Ensure that “users with similar responsibilities” have consistent access rights by defining permissions at the group level.

How to create and manage user groups:

1. Identify groups of users with common responsibilities or authority needs within the organization;
2. Determine the access required for each group;
3. Create the corresponding user group in the operating system or directory service;
4. Assign permissions to each group based on the principle of least privilege;
5. Add the relevant user to the corresponding group.

Avoid granting unnecessary write permissions

Restricting write permissions prevents files from being accidentally modified, unauthorized tampering, or triggering a data breach.

Be careful when granting write permissions: grant them only if the user really needs to modify the file, in most cases “read-only” permissions will suffice.

Guidelines for granting write permissions:

1. Follow the principle of least privilege: Write permission is granted only to the user or group that “really needs to modify the file/directory”;
2. Combining data attributes to determine: Key system files, configuration files or sensitive data should be strictly limited to write permissions to reduce the risk of unauthorized modifications;
3. Periodic review of adjustments: Ensure that write permissions are still in line with user responsibilities through regular audits and adjust redundant permissions in a timely manner;
4. Enabling File Version Control: Record file changes through versioning or backup mechanisms to facilitate restoration of historical versions when necessary;
5. Refinement of access restrictions: If supported by the operating system, this can be accomplished through file attributes, access control lists (ACLs) or file integrity mechanisms for finer control of write permissions.

Regularly back up and protect file permissions

Backup file permissions are a critical aspect of maintaining system integrity and security.

In the event of a system failure, data corruption or security incident, a full file permission backup ensures that access rights can be accurately restored.

How to securely store and restore file permissions:

• Incorporate file permissions into your regular data backup strategy;
• Determine the backup period for file permissions based on the frequency of system changes;
• Store permission backups in the same place as data backupsSeparate secure location；
• Encrypt privilege backups to prevent unauthorized access;
• Document the process of “Synchronized Restore of Privilege Backup and Data Backup”;
• Set up access control for privilege backups to limit unauthorized modifications;
• Regularly test the recovery process to verify the integrity and validity of privileged backups;
• Ensure that backup and recovery processes comply with relevant security standards and regulations;
• Keep documentation of backup and recovery operations for easy follow-up reference;
• For large systems, the backup and recovery process can be simplified with automated scripts.

Common File Permission Mistakes to Avoid

Understanding common misconfigurations of file permissions can help avoid potential security breaches and data leakage risks, and the following are key mistakes to avoid:

Granting Excessive Privileges

When assigning permissions to a file or directory, the principle of least privilege must be followed - that is, theGrant users only the minimum privileges needed to perform their tasks。

This approach significantly reduces the risk of unauthorized access or modification of sensitive data.

Practice Recommendations:

1. Carefully assess the access needs of each user or group and assign permissions as needed;
2. Periodically review and update permissions to ensure they match the user's current role.

Neglect of periodic authority audits

Regularly auditing file permissions is a necessary operation to maintain system security: over time, misconfigured or over-open permissions can accumulate and become vulnerabilities that can be exploited by unauthorized users.

ViaPeriodic authority auditsThis allows problems to be identified and corrected in a timely manner, ensuring that permissions are always in line with user responsibilities and that there are no unintended changes.

Practice Recommendations:

1. Record audit findings and rectify inconsistencies in authority in a timely manner;
2. (c) Establishing a mechanism for regularizing audits to avoid ignoring changes in authority for a long period of time after a “one-off audit”.

Using insecure default permissions

The default file permissions of a software application or system may not meet the specific security needs of the organization.

Therefore.Review and modify default permissionsIt is critical to match corporate security standards: evaluate the default settings and adjust them to a state that grants only the minimum necessary privileges.

Practice Recommendations:

1. After installing or updating the software/system, check and adjust the default permissions as a matter of priority;
2. Avoid using the default “open all permissions” configuration (e.g. 777 permissions) directly.

Confusing file ownership with permissions

Correctly distinguishing between “file ownership” and “file permissions” is a prerequisite for effective access control:

• possession: Refers to the users and groups associated with a file and determines “who has administrative control over the file.”
• scope of one's jurisdiction: Refers to the read, write, and execute permissions that different users or groups have on a file, defining “what operations can be performed on the file”.

Practice Recommendations:

1. Rationalization of ownership: Ensure that document owners are matched with actual management responsibilities;
2. Assigning permissions based on the principle of least privilege: Avoiding the problem of “permissions exceeding the scope of ownership control” due to confusion of the relationship between the two, and ensuring that access authorization can be controlled and traced.

Ignoring the granularity of file permissions

To achieve consistent access control, permissions must be set at a granular level - you can't just rely on broad global configurations, but you shouldSet permissions for individual files or directories individually according to specific needs。

Practice Recommendations:

1. Combine data sensitivity with user tasks to refine permission configurations;
2. Set strict permissions for highly sensitive files (e.g., financial data, private user information) separately to avoid “sharing a set of permission rules” with ordinary files.

Granting global or root level permissions

Granting “Global Privileges” or “Root Level Privileges” without a valid reason exposes the entire system to extremely high risk:

• global authority: Allow all users unlimited access to a file or directory;
• root level authority: Gives the user administrative control over the entire system.

Practice Recommendations:

1. Enhanced user education: Clearly inform users of the risks of such permissions and avoid granting them arbitrarily;
2. Strict authority for approval: Temporarily grant root-level access only when “absolutely necessary and there is no alternative” and document the purpose and time of the operation.

Lack of authority documentation

Complete documentation of file permission configurations and the logic behind them is the basis for efficient system management.

Lack of documentation can lead toDifficulty in subsequent troubleshooting and auditing of permissionsThe reason for this is that “no one knows the reason for the permission setting”, which can lead to misoperation.

Practice Recommendations:

1. Record all permission changes, including the time of the change, the person who performed the change, and the reason for the change;
2. Keep the overall description of the permission configuration to ensure that new administrators can quickly understand the permission design logic;
3. Incorporate permissions documentation into the system security documentation system and update it regularly.

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File Permissions and File Sharing

Understanding file permissions is central to enabling secure file sharing, and the following are key considerations:

1. Controlling the level of access

• read access: Allows the user to view the contents of a file, but not to modify or delete it;
• write access: Allow users to modify or delete files;
• execution authority: Valid only for executable programs or scripts, allowing the user to run the file.

The access control mechanism of the file system supports two types of permission assignments:

• Assign independent permissions to individual users;
• Bulk assignment of permissions via user groups (assign permissions to groups and then add users to the groups to simplify multi-user permissions management).

2. Shared folder permissions

When sharing folders, you need to make sure that the permissions are set appropriately.Accessible only to authorized users：

• Usually grant “read + write” privileges to the target user or group, while restricting access to other users;
• Regularly review and update shared permissions to avoid redundancy due to “user departure and role change” and to maintain data security.

3. Collaboration and group permissions

To improve team collaboration efficiency and streamline file sharing, you can create dedicated user groups:

• By “assigning permissions to groups” instead of “assigning permissions to individual users,” theBatch management of permissions；
• When a user joins a group, he or she automatically inherits the group's permissions without having to configure them one by one;
• Example: Create a “Marketing Collaboration Group” and grant read/write permissions to the “Marketing Materials Folder” for this group. New marketing employees can obtain the corresponding permissions by joining the group.

4. Access control lists (ACLs)

Access control lists (ACLs) provideMore granular permission control capabilities：

• Breaking through the traditional framework of “owner, group, other users”, it supports defining separate permissions for specific users or groups (e.g. “allow user A to read a file, but prohibit user B from reading the same file”);
• Suitable for complex scenarios (e.g., cross-departmental collaboration, external partner access), to meet the needs of “different users / groups need different permissions”.

5. Temporary access and expiration of privileges

When granting temporary access to files, you need to focus on “permission timeliness” to reduce security risks:

• Set a “time limit” (e.g., valid for 24 hours) or manually revoke permissions after a specific task is completed;
• assureGranting permissions only for the necessary period of timeThe risk of unauthorized access due to “permissions for a long time” (e.g., failure to retrieve partner's file permissions in a timely manner after the end of an external collaboration) is avoided.

6. Shared links and password protection

An additional layer of security can be added when sharing files via “Share Link” or “Password Authentication”:

• shared link: Generate unique, randomized links and avoid “easy-to-guess” links (e.g., links containing filenames);
• password protection: Set a password for the shared link and provide it only to authorized users;
• Timeliness control: Limit the validity of the link (e.g. within 7 days);
• Regularly review shared links and passwords, and expire “no longer in use” links in a timely manner to prevent disclosure.

7. Monitoring and auditing of shared documents

Regular monitoring and auditing is required to ensure that permissions on shared files are always as expected:

• fulfillmentPeriodic reviewIdentify and remove “expired, redundant” share permissions (e.g., share permissions for departing employees, temporary share permissions for completed projects);
• Maintain access logs for shared files to record “who accessed the file, when, and whether it was modified” for easy tracing of abnormal operations.

concluding remarks

File permissions are a core component of data security, through which precise control of “access, modification, and execution” of files and directories can be realized.

Understanding core concepts such as “read, write, and execute permissions” and “owner and group permissions” is the foundation for efficient file management and data security.

Unauthorized access and potential security breaches can be effectively prevented by properly configuring permissions and regularly reviewing updates.

In addition, it should be noted that: there are differences in the file permission mechanisms of different operating systems, you need to familiarize yourself with the specific configuration of the system used; at the same time, the combination of file permissions and encryption, regular backup and other measures, you can build a more comprehensive data security protection system.

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common problems

1. How are document permissions expressed?

There are two main ways to represent file permissions:

• symbolic representation: e.g. “rwxr-xr-x”, 9 characters in total, divided into 3 groups (3 characters per group), corresponding to “owner (u)” “group (g)” and “other user (o)” permissions respectively. “Other Users (o)” permissions. Among them, “r” = read, “w” = write, “x” = execute, “-” = no such permission (example) "rwxr-xr-x" means: owner has read/write/execute permissions, group and other users have read/execute permissions);
• numeric representation: e.g. 755, each digit corresponds to a set of permissions (owner, group, other users), and the permissions are calculated cumulatively as “read = 4, write = 2, execute = 1” (example 755: 7=4+2+1 (owner read/write/execute), 5=4+1 (group read/execute), 5=4+1 (other users read/execute)).

2. What are the different levels of authority?

There are three core permission levels with the following functions:

• Read access (r): Allows to view the contents of a file (e.g., open a text file, view an image); for directories, allows to view a list of files within a directory;
• Write permission (w): Allow modification of file contents (e.g., editing text, overwriting images), deletion of files; for directories, allow creation, deletion, and renaming of files within the directory;
• Execution authority (x): only for executable files (e.g. .exe programs, shell scripts), allowing the file to be run; for directories, allowing access to the directory (e.g. via thecdcommand to switch to that directory).

3. How do I set or modify file permissions?

There are two main modes of operation for different scenarios:

• Command line tools (for Unix-like systems, e.g. Linux, macOS): Usechmodcommand that supports symbolic or numeric representations (example:chmod 755 文件名(numerical representation),chmod u+rwx 文件名(symbolic representation to add read/write/execute permissions for the owner));
• Graphical User Interface (for Windows, macOS and Linux with desktop environment): Right-click the file/directory, select “Properties” (Windows) or “Show Profile” (macOS), and in the “Permissions” or “Sharing and Permissions” panel, directly check/uncheck the “Read” and “Write” permission options, or add/remove authorized users.

4. Can document permissions be inherited?

Yes, file permissions can be inherited from a parent directory, a mechanism that simplifies the management of permissions for multiple files/directories:

• Succession rules: When a new file or directory is created, it inherits the permissions of the parent directory by default (e.g., if the parent directory has permissions of 755, the default permissions for a new file may be 644 - because files do not have execute permissions by default, and directories have execute permissions by default);
• Special Configurations: Some systems (e.g. Linux) can be accessed via thesetgidPermissions (set for directories)chmod g+s) Enhanced Inheritance Effect -- Enables newly created files/directories within a directory to automatically inherit the group ownership of the parent directory instead of the creator, for team sharing scenarios.

5. How do I check file permissions?

The different operating systems are viewed as follows:

• Unix-like systems (Linux, macOS)：
  1. Open the terminal;
  2. importationls -l 文件名/目录名(For example,ls -l document.txt), the “-rwxr-xr-x” part of the output is the permissions (e.g.-rwxr-xr-x 1 user group 1024 Feb 5 14:00 document.txt）；
• Windows system：
  1. Right-click on the file / directory and select “Properties”;
  2. Switch to the “Security” tab and select the target user/group in the “Groups or Usernames” list to view the permissions it has (e.g. “Read and Execute” “Write”);
• macOS system：
  1. Right click on the file / directory and select “Show Profile”;
  2. Scroll down the “Sharing & Permissions” panel to view the permissions for each user/group in the user list (e.g. “Read” “Write” “Read Only ”).

6. What problems can result from misconfigured file permissions?

Misconfiguration of permissions can cause a variety of security and functionality issues, notably:

• Unauthorized access: If sensitive file permissions are set to “readable by other users (r)”, this results in unauthorized persons viewing private data (e.g., user password files, financial statements);
• Data loss/corruption: If the permissions of critical system files are set to “other users can write (w)”, they may be deleted or tampered with by mistake (e.g., modification of the system configuration file resulting in a service crash);
• system vulnerability: If the permissions of an executable file are set to “globally executable (x)”, it may be exploited to implant malicious code (e.g., a hacker runs a Trojan horse program by modifying the permissions);
• functional abnormality: If a user does not have “execute permission (x)” to run the necessary applications, or “enter directory permission (x)” to access the working files in the directory.