Tag

firewall

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Raymond Ops
Raymond Ops
Jun 13, 2025 · Information Security

Master Ubuntu’s UFW: Simple Commands to Enable, Configure, and Manage Firewall Rules

This article introduces Ubuntu’s Uncomplicated Firewall (UFW), explaining how to enable, disable, reset, set default policies, and create, modify, or delete specific IP, port, and protocol rules using concise command-line examples, helping users quickly secure client machines with practical firewall configurations.

LinuxUFWcommand line
0 likes · 7 min read
Master Ubuntu’s UFW: Simple Commands to Enable, Configure, and Manage Firewall Rules
IT Xianyu
IT Xianyu
Apr 27, 2025 · Operations

How to Migrate from CentOS 7 to AlmaLinux 8 and AlmaLinux 9: A Step‑by‑Step Guide

After CentOS 7 reaches end‑of‑life on June 30 2024, this guide explains why you must migrate, outlines three essential pre‑migration preparations, and provides detailed step‑by‑step commands to upgrade first to AlmaLinux 8 and then to AlmaLinux 9, including post‑migration checks and common pitfalls.

AlmaLinuxCentOSLeapp
0 likes · 8 min read
How to Migrate from CentOS 7 to AlmaLinux 8 and AlmaLinux 9: A Step‑by‑Step Guide
Java Architect Essentials
Java Architect Essentials
Apr 20, 2025 · Information Security

Free PC Firewall Recommendations and Comparative Analysis

This article provides a comprehensive comparison of free PC firewall solutions, detailing each software's core functions, suitable scenarios, drawbacks, and source references, followed by key recommendations, compatibility notes, performance assessments, and user feedback to help readers choose the most suitable firewall.

PC securitySoftware Comparisonfirewall
0 likes · 14 min read
Free PC Firewall Recommendations and Comparative Analysis
Raymond Ops
Raymond Ops
Apr 8, 2025 · Operations

How to Log Dropped iptables Packets for Input and Output Traffic

Learn step‑by‑step how to configure iptables to log all dropped inbound and outbound packets to syslog, including creating a LOGGING chain, setting rate limits, customizing log prefixes, directing logs to a specific file, and interpreting the resulting log entries.

Linuxfirewalliptables
0 likes · 7 min read
How to Log Dropped iptables Packets for Input and Output Traffic
Raymond Ops
Raymond Ops
Mar 24, 2025 · Operations

Master Reverse SSH Tunneling: Seamlessly Access Firewalled Servers

This guide explains what reverse SSH tunneling is, why it’s needed to reach servers behind firewalls, and provides step‑by‑step commands and configuration tips—including the use of the ssh -R option, setting up a persistent machine, and essential sshd settings.

SSHfirewallremote access
0 likes · 6 min read
Master Reverse SSH Tunneling: Seamlessly Access Firewalled Servers
Efficient Ops
Efficient Ops
Mar 12, 2025 · Information Security

30 High-Risk Ports You Must Secure and How to Close Them

This guide lists 30 commonly exposed high‑risk ports such as LDAP, MySQL, and Docker, explains the security threats they pose, and provides practical firewall, service‑management, and port‑closing steps—including command‑line examples—to help you harden your systems against attacks.

Network Securityfirewallhigh-risk ports
0 likes · 7 min read
30 High-Risk Ports You Must Secure and How to Close Them
Raymond Ops
Raymond Ops
Dec 17, 2024 · Information Security

Mastering firewalld vs iptables on CentOS 7: Zones, Rules, and Configuration

This guide explains the differences between firewalld and iptables on CentOS 7, introduces zone management, details iptables packet flow, tables, chains, and provides practical commands for installing, configuring, and managing firewall rules, including examples for SSH and ping traffic.

CentOS7LinuxNetwork Security
0 likes · 12 min read
Mastering firewalld vs iptables on CentOS 7: Zones, Rules, and Configuration
Deepin Linux
Deepin Linux
Nov 13, 2024 · Information Security

Understanding Netfilter and iptables: Architecture, Hook Mechanism, and Configuration in Linux

This article provides a comprehensive overview of Linux's Netfilter framework and its iptables user‑space tool, explaining their hook‑based architecture, core data structures, rule tables and chains, common configuration commands, practical use cases, and both strengths and limitations for network security.

LinuxNetwork Securityfirewall
0 likes · 35 min read
Understanding Netfilter and iptables: Architecture, Hook Mechanism, and Configuration in Linux
Practical DevOps Architecture
Practical DevOps Architecture
Aug 21, 2024 · Information Security

Step-by-Step Guide to Installing and Configuring iptables on Linux

This article provides a comprehensive, step-by-step tutorial on checking, installing, editing, and applying iptables firewall rules on a Linux system, including common port allowances, ICMP handling, rule persistence, and startup configuration using command-line examples.

LinuxSystem Administrationfirewall
0 likes · 6 min read
Step-by-Step Guide to Installing and Configuring iptables on Linux
DevOps Operations Practice
DevOps Operations Practice
Jul 14, 2024 · Information Security

Introduction to iptables: Concepts, Commands, and Practical Use Cases

This article introduces iptables, explains its core concepts such as chains, rules, and tables, demonstrates common command‑line operations for displaying, adding, deleting and modifying rules, and presents a real‑world firewall configuration example for securing jump‑servers on CentOS.

LinuxNetwork Securitycommand line
0 likes · 9 min read
Introduction to iptables: Concepts, Commands, and Practical Use Cases
Java Tech Enthusiast
Java Tech Enthusiast
May 5, 2024 · Information Security

Preventing Malicious API Abuse: Security Measures and Best Practices

To prevent malicious API abuse, implement layered defenses such as firewalls to block unwanted traffic, robust captchas and SMS verification, mandatory authentication with permission controls, IP whitelisting for critical endpoints, HTTPS encryption, strict rate‑limiting via Redis, continuous monitoring with alerts, and an API gateway that centralizes filtering, authentication and throttling.

API securityIP whitelistRate Limiting
0 likes · 9 min read
Preventing Malicious API Abuse: Security Measures and Best Practices
Selected Java Interview Questions
Selected Java Interview Questions
Feb 29, 2024 · Information Security

How to Prevent Malicious API Abuse: Firewalls, Captchas, Authentication, IP Whitelists, Encryption, Rate Limiting, Monitoring, and Gateways

This article explains a comprehensive set of techniques—including firewalls, captchas, authentication checks, IP whitelists, data encryption, rate limiting, monitoring, and API gateways—to protect interfaces from malicious abuse and ensure secure, reliable service operation.

API securityAuthenticationRate Limiting
0 likes · 12 min read
How to Prevent Malicious API Abuse: Firewalls, Captchas, Authentication, IP Whitelists, Encryption, Rate Limiting, Monitoring, and Gateways
Java Tech Enthusiast
Java Tech Enthusiast
Jan 21, 2024 · Information Security

Security Risks of Exposing Your Public IP Address

Exposing your public IP address can invite DDoS floods, vulnerability scanning, privacy breaches, and targeted phishing or malware attacks, so you should protect it with firewalls, regular updates, secure VPN connections, and by avoiding public disclosure on social platforms.

DDoSNetwork Securityfirewall
0 likes · 3 min read
Security Risks of Exposing Your Public IP Address
IT Services Circle
IT Services Circle
Jan 17, 2024 · Operations

Common Reasons Why Cloud Server Ports Are Unreachable and How to Fix Them

This article lists the most frequent causes—such as an unstarted application, incorrect port listening, cloud security‑group settings, firewall rules, application‑level IP restrictions, network problems, and user‑side issues—and provides step‑by‑step commands and screenshots to help troubleshoot and restore access to cloud server ports.

Security GroupTroubleshootingcloud
0 likes · 8 min read
Common Reasons Why Cloud Server Ports Are Unreachable and How to Fix Them
Laravel Tech Community
Laravel Tech Community
Oct 24, 2023 · Information Security

Configuring Firewalld on CentOS to Restrict Access to Specific Ports and IP Addresses

This article explains what Firewalld is, outlines its key features such as zones, runtime versus permanent settings, services, and dynamic updates, and provides step‑by‑step commands to create firewall rules that limit access to an Nginx server on port 8088 to a single IP address while leaving other ports unrestricted.

CentOSLinuxNetwork Security
0 likes · 8 min read
Configuring Firewalld on CentOS to Restrict Access to Specific Ports and IP Addresses
DeWu Technology
DeWu Technology
May 19, 2023 · Operations

Investigation and Resolution of In‑flight Wi‑Fi Connectivity Issues for a Mobile E‑Commerce App

The SRE team diagnosed an in‑flight Wi‑Fi outage for the DeWu e‑commerce app by reproducing the problem, capturing packets with ping, traceroute and tcpdump, discovered a firewall rule misclassifying the domain as a download site, and resolved it through a vendor‑issued policy update, restoring connectivity on both ATG and SATCOM links.

SRETCPWiFi
0 likes · 18 min read
Investigation and Resolution of In‑flight Wi‑Fi Connectivity Issues for a Mobile E‑Commerce App
360 Tech Engineering
360 Tech Engineering
Apr 19, 2023 · Databases

ProxySQL Overview: Core Features, Configuration Layers, and Practical Use Cases

This article introduces ProxySQL as a high‑performance MySQL proxy, explains its request flow, multi‑layer configuration system, key tables, and demonstrates practical scenarios such as read‑write splitting, hostgroup weight tuning, replication‑lag handling, blacklist/whitelist rules, and firewall protection.

Database ProxyMySQLProxySQL
0 likes · 26 min read
ProxySQL Overview: Core Features, Configuration Layers, and Practical Use Cases
DevOps Operations Practice
DevOps Operations Practice
Mar 8, 2023 · Information Security

Introduction to iptables: Concepts, Commands, and Practical Use Cases

This article introduces iptables, explains its core concepts such as chains, rules, and tables, demonstrates common commands for listing, adding, deleting, and modifying rules, and presents a step‑by‑step firewall configuration case for securing jump‑hosts on CentOS systems.

CentOSLinuxNetwork Security
0 likes · 8 min read
Introduction to iptables: Concepts, Commands, and Practical Use Cases
Efficient Ops
Efficient Ops
Feb 1, 2023 · Information Security

How a Misconfigured Kubelet Led to a Crypto‑Mining Breach and How to Secure Your Cluster

The article recounts a Kubernetes cluster intrusion where a misconfigured kubelet allowed crypto‑mining, details the forensic steps taken—including empty iptables, kubelet API exposure, and commented‑out settings—and offers concrete hardening recommendations to prevent similar attacks.

Cluster HardeningKubernetescrypto mining
0 likes · 5 min read
How a Misconfigured Kubelet Led to a Crypto‑Mining Breach and How to Secure Your Cluster
Practical DevOps Architecture
Practical DevOps Architecture
Dec 26, 2022 · Information Security

Understanding iptables: Tables, Chains, and NAT Operations

This article provides a comprehensive overview of iptables, detailing its host‑type filter table, limitations, the four main tables (filter, nat, mangle, raw), their respective chains, common command examples, and explains NAT concepts such as SNAT, DNAT, and MASQUERADE for Linux network security.

LinuxNATNetwork Security
0 likes · 6 min read
Understanding iptables: Tables, Chains, and NAT Operations