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...

Do Not Use X11 Forwarding

The X11 forwarding function of SSH allows the GUI program of the remote host to be executed on the local host. If the X11 forwarding function is enabled, the attack surface is expanded and other users on the X11 server may attack the local host. If the function is not required in the service...

Ensure That All Groups Exist in /etc/passwd

All user groups in /etc/passwd must exist in the /etc/group file. If the administrator manually modifies the two files, the user groups may be incorrectly set due to human errors. If a user group in /etc/passwd does not exist in /etc/group, risks of user group permission management may occur...

Do Not Install Network Sniffing Tools

If network sniffing tools exist in the production environment, attackers may use them for network analysis and attacks. Therefore, in the production environment, do not install network sniffing, packet capturing, or analysis tools, such as tcpdump, Ethereal, and Wireshark. SPDX-FileCopyrightText:...

Do Not Install the FTP Client

File Transfer Protocol FTP is used for file transfer between a Linux server and other servers, desktop systems, as well as terminal devices. FTP does not support encrypted transmission. As a result, data can be easily stolen by attackers during transmission. Therefore, do not install FTP clients ...

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...

Do Not Install the NIS Client

Network Information Service NIS works in client-server mode. NIS clients running the ypbind daemon obtain information from a server. NIS is inherently insecure and is vulnerable to DoS and buffer overflow attacks. Therefore, do not install the NIS client in the service scenario where NIS is not...

Do Not Install the Telnet Client

Telnet is an application-layer protocol and is usually used for remote login, operation control, and system modification of servers. Telnet data is not encrypted, and user names, passwords, and transmitted data can be easily stolen by attackers. Therefore, do not install or use Telnet clients. Us...

Configure the dmesg Access Permission Properly

The permission to access dmesg information is restricted. Unprivileged users cannot view system information. This prevents any one from obtaining sensitive information and attacking the system. Only processes with the CAPSYSLOG capability are allowed to access kernel logs. In this way, the least...

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...

Do Not Install Python 2

The EOL for Python 2 was reached on January 1, 2020, and there will be no updates and maintenance. If you continue to use Python 2, the system attack surface may be expanded, and system vulnerabilities and attack risks may increase. Therefore, do not use Python 2. If Python is required, you are...

Do Not Install the Print Service

A server running Common Unix Printing System CUPS provides print services to other devices on the network. Running the CUPS service requires additional system resources and expands the attack surface. Therefore, do not start the CUPS service in the scenario where the CUPS service is not required...

Discard Forged ICMP Packets and Do Not Record Logs

Setting icmpignoreboguserrorresponses to 1 prevents the kernel from recording responses to duplicate broadcast packets, which prevents useless log information from filling in the file system. Some attackers send ICMP packets that violate RFC-1122 and attempt to fill the log file system with a lar...

Enable Kernel SMAP

Supervisor Mode Access Prevention SMAP can be enabled to prevent the kernel from accessing data in user space. If SMAP is not enabled, attackers can access data in user space through kernel-mode code redirection, which increases the attack surface and reduces system security. SMAP is enabled by...

Ensure That the Password Protection Is Configured in Single-User Mode

You can edit the GRUB startup menu and add the s or single command to the Linux startup command line to enter the single-user mode, which is an emergency rescue mode. In this mode, system data can be modified. For example, users can change the password of the root user. In this case, the password...

Ensure That Users Are Required to Change Their Passwords Upon the First Login

If a password, such as one reset by an administrator, is not promptly changed in the service environment when it is not set by the user, it may lead to low-cost attacks. Therefore, it is necessary for users to change their password upon their initial login. However, the root user...

Huawei EulerOS: Security Advisory for python3 (EulerOS-SA-2025-1436)

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...

Disable IP Forwarding

If a node does not function as a gateway server, disable the IP forwarding function. Otherwise, attackers can use the node as a router. In the container scenario, if network packets need to be forwarded through the host, IP forwarding is allowed. SPDX-FileCopyrightText: 2025 Greenbone AG Some tex...

Do Not Install the rsync Service

The rsync service can synchronize data between servers or between local drive partitions. However, information leakage risks exist because rsync uses non-encrypted transmission protocols. If the rsync service is enabled and data is transmitted between servers over the network, attackers can...

Do Not Install the HTTP Service

HyperText Transfer Protocol HTTP is a simple request-response protocol and usually runs over TCP. It specifies what messages the client may send to the server and what responses the client receives. Request and response messages include headers in ASCII, and the message content often uses a...