Configure the SSH Service Log Level Properly

SSH provides multiple log output levels, such as QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. A higher log level such as QUIET or FATAL prints less log information. This saves drive space but hinders administrators from auditing and tracing SSH events. Conversely, a lowe...

Configure the Default Policies of nftables to DROP Properly

For security purposes, the nftables base chains INPUT, OUTPUT, and FORWARD are similar to those of iptables. You need to configure the DROP policy for all packets, and then add the ACCEPT policy to the base chains to open related services and ports. If the base chains are not configured or the ho...

Ensure a Firewall Service is Enabled

A firewall is a fundamental security control that enforces mandatory access between networks or systems. Without a firewall, systems are exposed to unauthorized access, data theft, tampering, bandwidth abuse, and malicious traffic. Linux commonly provides three firewall services: firewalld defaul...

Ensure That the Number of Files That Can Be Opened by Users Is Correctly Configured

The number of files that can be opened in Linux is limited. Once the limit is reached by a user, other users can no longer open files. By default, openEuler limits the maximum number of file handles that can be opened by each user to 1024. If the value exceeds 1024, new file handles cannot be...

Configure Proper Policies for INPUT of iptables

The INPUT chain is used to filter packets received from external systems. For any service provided for external systems, configure the corresponding INPUT policy and enable the related port so that external clients can access the service through the port. If the policy is not set, all packets tha...

Configuring the SSH Service Port Properly

A server typically has multiple NICs and IP addresses. You need to plan IP addresses to determine which ones are used for services or management. Not all IP addresses need to listen on SSH connections. You can specify only some IP addresses to perform SSH connections to reduce the attack surface...

Configure a Proper Value for LoginGraceTime

LoginGraceTime is used to limit the login time of a user. If a user does not complete the login within the time specified by LoginGraceTime, the connection is automatically disconnected. You are advised to set this field to a value less than or equal to 60, in seconds. If this field is set to a...

Enable the rsyslog Service

System logs are stored in the memory by default. If the rsyslog service is disabled, system logs cannot be dumped to persistent storage devices and will be lost after the system is restarted. The rsyslog service is used to dump and distribute system logs, supporting the following functions: 1...

Configure a Proper Value for MaxAuthTries

MaxAuthTries indicates the maximum number of user authentication failures allowed in a single connection. If the number of user authentication failures exceeds the value, the connection is automatically disconnected. You are advised to set this field to a value less than or equal to 3. If this...

Ensure That the umask Value Is Correct

The umask value is the mask for default file or directory permissions. When a file or directory is created, its default permission is set to 777 minus the umask value. For a file, its execute permission is also removed. If the umask value is set improperly, the permission of new files may be too...

Configure the Kernel Parameter ptrace_scope Properly

ptrace is a system call used for process tracing. It provides the capability for a parent process to observe and control child processes. Linux Kernel 3.4 and later versions support completely restricting or disabling the ptrace function. According to the Linux Kernel Yama Documentation, the...

Ensure That the PATH User Variable Is Strictly Defined

In Linux, the PATH variable defines the path for searching for executable files in the user context of the current user. For example, if a user runs the ls command in any directory, the system searches for the ls command in the directories specified by PATH and executes the command. The PATH...

Correctly Configure the Default File Permission For rsyslog

Log files record system behaviors. The rsyslog log tool records logs in specified files. When the specified log file does not exist in the system, rsyslog creates a log file. The permission of the created log file can be configured in the rsyslog configuration file. The configuration of the defau...

Ensure That the Security Level of the Global Encryption Policy Is Not Lower than DEFAULT

The global encryption/decryption policy of the system is used to specify the algorithms supported by the encryption and decryption components. You can change the preset security policy level by modifying the /etc/crypto-policies/config configuration file to change the algorithm set that can be us...

Configure a Correct SSH Service Version

SSH1 contains known issues and is no longer maintained in a routine manner, which poses risks such as information leakage and command data tampering on the system. The OpenSSH component inherited by openEuler uses the SSH protocol for remote control or file transfer between servers. The SSH1.3,...

Configure a Proper Number of Concurrent Sessions Allowed for a Single SSH Connection

SSH allows a client that supports multiplexing to establish multiple sessions based on a network connection. MaxSessions limits the number of concurrent SSH sessions that can be established for each network connection. This prevents system resources from being occupied by a single connection or a...

Configure the Core Dump Properly

A core dump records the memory status when a program stops abnormally or breaks down. It helps locate faults but may contain sensitive information in the process memory. In some cases, the core dump function needs to be enabled to record problem causes. When enabling the core dump function,...

Configure a Proper Value for audit_backlog_limit

auditbackloglimit sets the buffer queue length for audit events awaiting transfer to the audit service. The default value is 64. If the queue is full, audit events are discarded and an alarm log is generated, indicating that the queue is full. If the value is too small, audit events may be lost. ...

Ensure That a User Is Locked After a Specified Number of Login Failures

If a user fails to log in to the system for a specified number of consecutive times, the system locks the user. That is, the user is not allowed to log in to the system for a specified period of time to prevent malicious system password cracking. During the lockout period, any input is considered...

Do Not Enable Login Capabilities for Users Who Are Not Meant for Direct Login

Typically, a Linux system has multiple users, not all of which are used for login. For instance, some users are automatically created during the installation of software packages like systemd and dhcp. These users serve specific purposes, such as running related software services. It is essential...