Avoid Using USB Storage

USB storage devices are usually used to transfer data between servers. However, in most cases, data on USB storage devices cannot be protected by technical methods, thereby increasing the risk of attacks. Viruses and Trojan horses on USB devices may infect and damage the server. If the USB storag...

Configure Kernel Parameter kptr_restrict Properly

kptrrestrict is used to protect kernel symbol addresses. When the protection level is low, common users can obtain kernel symbol addresses, which are easy to be exploited by attackers. This increases the attack surface and reduces system security. Currently, kptrrestrict can be set to any of the...

Ensure That the Password Protection Is Configured for GRUB

GRUB is the default bootloader of Linux. The bootloader can set the startup mode of the system. By setting the GRUB password, you can prevent attackers from modifying the GRUB setting to enter the single-user mode. If the GRUB password is not set, attackers can easily access the GRUB editing menu...

Do Not Enable the DNS Service

The Domain Name System DNS is a hierarchical naming system that maps names to IP addresses of computers, services, and other network resources. Unless a system is the designated DNS server, you are advised to disable its DNS service to reduce the attack surface. SPDX-FileCopyrightText: 2025...

Ensure That Old Passwords Are Verified When Users Change Them

To prevent a third party from maliciously changing the password of another user, the old password must be verified when a user changes the password. According to the common practice in the industry, the old password does not need to be verified when the root user changes its own password. The roo...

Ensure That GPG Verification Is Configured for the Yum Repositories

Software packages may be tampered with by attackers during network transmission or local storage. If the integrity verification is not performed on the software packages, software tampered with by attackers may be installed. As a result, the server or even the entire network cluster is attacked. ...

Restrict the Number of Historical Command Records

HISTSIZE is an environment variable used to control the size of the command history. Specifically, HISTSIZE defines the number of command entries that can be stored in the command history. By setting the value of HISTSIZE, you can limit or increase the size of the command history, thus controllin...

Log Spoofing Source Routing and Redirect Packets

Logging spoofing, source routing, and redirect packets sent to the system helps discover attack sources and formulate protection measures. SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted from a referenced sources, and are Copyright C by the respective right...

Configure sudoers Audit Rules

The sudo command allows common users to perform privileged operations as the root user, which is highly risky. Though attackers cannot access the root user easily, they can escalate the privilege using the sudo command. You are advised to configure audit for the /etc/sudoers file and the...

Configure Audit Rules for File Access Control Permissions

File access permission control is the basic permission management in Linux. Different users can access different files after being authorized. This prevents sensitive information leakage or file data tampering between users and prevents common users from accessing high-permission files or...

Do Not Use Historical Passwords

Using the same historical password frequently may cause password leakage and attacks. To ensure user security, the function of disabling historical passwords must be configured. The number of historical passwords that cannot be used must be properly set based on the actual service scenario. The...

Configure a Proper Number of Queues in the SYN_RECV State

The SYNRECV queue stores the TCP connection requests that have not been confirmed by the peer end. A larger value indicates more waiting network connections. If the value is too small, the system is vulnerable to TCP SYN flood attacks. As a result, normal connections are denied. If the value is t...

Configure TIME_WAIT for TCP

TIMEWAIT indicates the time for TCP to wait for connection destruction. If this parameter is set to a large value, a large number of TCP connections are not closed and DoS attacks occur. You are advised to set this parameter to a value less than or equal to 60. SPDX-FileCopyrightText: 2025...

Ensure That the Password Validity Is Set Correctly

If a password is not changed for a long time, the password is vulnerable to brute force cracking, which compromises system security. If the password validity period is set too short, the password needs to be changed frequently, increasing management costs. In addition, users may fail to log in...

Configure Audit Rules for Kernel Module Changes

Generally, for deployed services, the loaded kernel modules do not change. Therefore, changes in loaded kernel modules may indicate attacks. You are advised to audit and monitor kernel module changes for future tracing. By default, audit rules for kernel module changes are not configured in...

Ensure That Partitions without Executable Files Are Mounted Using noexec

A data drive only stores data generated during service running. No command is executed in the data drive. Therefore, you can mount the drive or partition using noexec to improve security and reduce the attack surface. SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be...

Configure Proper Policies for INPUT of nftables

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...

Do Not Install Insecure SNMP Versions

Simple Network Management Protocol SNMP is a standard protocol designed to manage network nodes in IP networks. This protocol allows the exchange of network management and control data between network elements NEs. If SNMP is installed in scenarios where SNMP is not required, additional system...

Do Not Install the TFTP Client

Trivial File Transfer Protocol TFTP is used for file transfer between a Linux server and other servers, desktop systems, as well as terminal devices. TFTP does not support authentication and encryption mechanisms. Data tends to be forged, tampered with, or stolen by attackers during communication...

Configure a Proper SSH Service Authentication Mode

A proper authentication mode helps ensure user and system data security. Typically, the user/password authentication mode is suitable for human-machine users. In non-interactive login scenarios, the public and private keys are suitable for authentication. In high-risk scenarios, only the public a...

Configure at and cron Services Properly

The at service is used to execute simple tasks once, and the cron service is used to execute periodic and scheduled tasks. In the cron command, the /etc/cron.deny file is the blocklist configuration file, and the /etc/cron.allow file is the allowlist configuration file, which is absent by default...

Enable Reverse Path Filtering

Setting net.ipv4.conf.all.rpfilter and net.ipv4.conf.default.rpfilter to 1 forces the Linux kernel to perform reverse path filtering on a received packet and check the validity of its source address. If the Linux kernel queries the routing table in which the source address is included and finds...

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...

Configure Audit Rules for File Access Failures

System calls, such as open, truncate, ftruncate, create and openat, are audited and monitored. If the -EACCES or -EPERM error is returned, you lack the permission to access the files. In this case, audit logs need to be recorded. File access failures due to a lack of proper permissions are common...

Avoid the .forward File in the Home Directory

An email address can be configured in the .forward file. When a user receives an email, the email is automatically forwarded to the email address. If there are no email forwarding scenarios, you are advised to delete the .forward file. If the .forward file exists, emails containing sensitive...

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...

Configure Audit Rules for File Deletion

Generally, it is highly risky to delete files in the OS. Misoperations by administrators or attacks may cause severe system faults. You are advised to audit and monitor system calls, such as rename, unlink, unlinkat, and renameat, and record deletion operation logs. Deleting system or service fil...

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,...

Do Not Allow Globally Writable Files

Globally writable files can be written by any user in the system, which is generally not needed. If a file is improperly set to globally writable, the file can be easily tampered with by attackers, causing security risks. Therefore, if a file is required to be globally writable, the actual scenar...

Do Not Allow Login with an Empty Password

Login with an empty password means that a user can log in to a system without a password. If an empty password is allowed for login, the user with an empty password may be attacked or may be used by attackers. SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted fro...

Ensure That Partitions That Do Not Need to Be Mounted with Devices Are Mounted Using nodev

The nodev option specifies that the file system cannot contain device files. It is used to reduce the attack surface and improve security. If a directory is mounted with the nodev option, all device files, such as files of block devices and character devices in the directory, are parsed as common...

Enable the enforcing Mode

SELinux is a built-in security module in Linux distributions. It controls the access from applications to resources in a fine-grained way, thus improving system security. SELinux can run in any of the following modes: 1. enforcing: If the user does not have the permission to access the resource,...

Avoid Enabling Unnecessary Services and Ports

In the zones, you need to specify the interfaces, ports, and services that need to be enabled or disabled. Correct configuration prevents illegitimate packets from being received and processed, reduces the number of exposed ports on the server, and reduces the attack surface. If the configuration...

Ensure That the su Command Inherits the User Environment Variables Without Escalating Privileges

The su command enables a common user to have the permissions of the superuser or other users. It is often used for switching the user from a common user to the root user. The su command provides a convenient way for users to change their identities. However, if the su command is run without...

Configure Audit Rules for Time Changes

The system time is essential for the normal running of services. The system time can be changed through synchronization with the time server and manual operations of administrators. The latter is prone to attacks because attackers can change the system time to invalidate some protection policies...

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...

Avoid Using the root User to Access the System Locally

Users with the root permission can access all Linux resources. If the root user is used to log in to the Linux OS to perform operations, there are many potential security risks. To avoid the risks, do not use the root user to log in to the Linux OS. If necessary, indirectly use the root user...

Disable the Source Packet Routing

In a network, source routing allows the sender to specify some or all routes for data packets to pass through the network. In regular routing, routers in the network determine the path based on the destination of the data packets. If a large number of packets are tampered with and pass through th...

Configure Session Audit Rules

You are advised to audit and monitor the /var/run/utmp, /var/log/wtmp, and /var/log/btmp files. /var/run/utmp records all login events, /var/log/wtmp records all login, logout, shutdown, and restart events, and /var/log/btmp records login failure events. If session audit is not configured,...

Enable PAM Authentication

Pluggable Authentication Modules PAM on the Linux platform provides a series of open source shared library files .so files. You can flexibly control the authentication process by configuring parameters. After PAM authentication is configured for SSH, the user authentication management module of t...

Configure The ntpd Service Properly

In the cluster scenario, the time of servers must be accurate and consistent. For example, if the server time is inconsistent, the data generated by different servers may be sorted or compared inaccurately. Even if you run the date command to set the time of all servers to the same value, the tim...

Ensure That Rotation Is Enabled for Audit Logs

maxlogfileaction decides the action taken when the size of a log file reaches the upper limit. By default, ROTATE is configured in openEuler, indicating that a new log file is created when the size of a log file reaches the upper limit and the original log file is not deleted. numlogs specifies t...

Do Not Allow Hidden Executable Files

In Linux, the name of a hidden file starts with a dot .. Hidden executable files are not allowed in the system. Note that . and . are not hidden files. They refer to the current directory and upper-level directory, respectively. The .bashrc, .bashprofile, and .bashlogout files are script files us...

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 a Proper SSH Service Authentication Mode

A proper authentication mode helps ensure user and system data security. Typically, the user/password authentication mode is suitable for human-machine users. In non-interactive login scenarios, the public and private keys are suitable for authentication. In high-risk scenarios, only the public a...

Huawei EulerOS: Security Advisory for krb5 (EulerOS-SA-2025-1424)

The remote host is missing an update for the Huawei EulerOS SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted from a referenced sources, and are Copyright C by the respective right holders. SPDX-License-Identifier: GPL-2.0-only ifdescription...

Huawei EulerOS: Security Advisory for openssh (EulerOS-SA-2025-1429)

The remote host is missing an update for the Huawei EulerOS SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted from a referenced sources, and are Copyright C by the respective right holders. SPDX-License-Identifier: GPL-2.0-only ifdescription...

Huawei EulerOS: Security Advisory for libtasn1 (EulerOS-SA-2025-1425)

The remote host is missing an update for the Huawei EulerOS SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted from a referenced sources, and are Copyright C by the respective right holders. SPDX-License-Identifier: GPL-2.0-only ifdescription...

Huawei EulerOS: Security Advisory for git (EulerOS-SA-2025-1415)

The remote host is missing an update for the Huawei EulerOS SPDX-FileCopyrightText: 2025 Greenbone AG Some text descriptions might be excerpted from a referenced sources, and are Copyright C by the respective right holders. SPDX-License-Identifier: GPL-2.0-only ifdescription...