security

Set up DMARC (verification) for Postfix on Debian server

This tutorial will be showing you how to set up OpenDMARC with Postfix SMTP server on Debian/Ubuntu server to block email spoofing and spam.

Security Networking

DMARC - Domain-based Message Authentication, Reporting and Conformance

Domain-based Message Authentication, Reporting, and Conformance, or DMARC, is a technical standard that helps protect email senders and recipients from spam, spoofing, and phishing...

Networking Security

Explanation DKIM (DomainKeys Identified Mail) in all details

DKIM (DomainKeys Identified Mail) is a system that lets your official mail servers add a signature to headers of outgoing email and identifies your domain’s public key so other mail servers can verify the signature. As with SPF (Sender Policy Framework helps keep your mail from being considered spam. It also lets mail servers detect when your mail has been tampered with in transit.

Networking Security

SPF - Sender Policy Framework

Sender Policy Framework (SPF) is an email authentication method designed to detect forged sender addresses in emails (email spoofing), a technique often used in phishing and email spam. SPF allows the receiver to check that an email claiming to come from a specific domain comes from an IP address authorized by that domain's administrators.

Networking Security

What is email envelope and email header

The key for understand smtp protocol is learn, what is difference between email envelope and email header. Another words, what is email envelope vs email header.

Networking Security

Certbot and Let’s Encrypt CA

What is Certbot, cerbots commands and user guide, what is Let's Encrypt Rate Limits. How works cerbot authenticators and installers, certbot commands exmaples

Linux Security Web Servers

OCSP Stapling on Nginx and Apache webserver

To understand OCSP stapling, it is necessary to understand OCSP, the Online Certificate Status Protocol. OCSP is a protocol for determining whether a certificate is revoked (for instance, becau se its private key was compromised). Every time a browser connects to an HTTPS website, it contacts the OCSP responder specified in the SSL certificate, and asks if the certificate is revoked. If the respond er replies that the certificate is revoked, the browser blocks the page from loading.

Web Servers Networking Security

nftables geoip - continents ip

In the previous articles, we showed how to perform packet marking in nftables based on geoip source ip addresses and also how to log traffic to external files .
Today we will show how to mark packets based on which continent they come from.

The principle is that we first mark packets based on the source IP address so that we know which countries they are coming from. And then we'll find out which continent the state is on.

Linux Security Networking

nftables and GeoIP

We'll learn how we can block traffic originated from specific country or continent IPs using GeoIP database and linux nftables . This article describes the configuration for debian linux distros. nftables is the new packet classification framework that intends to replaces the existing {ip,ip6,arp,eb}_tables infrastructure. In a nutshell:

It is available in Linux kernels >= 3.13
It comes with a new command line utility nft whose syntax is different to iptables.
It also comes with a compatibility layer that allows you to run iptables commands over the new nftables kernel framework.
It provides generic set infrastructure that allows you to construct maps and concatenation. You can use this new feature to arrange your ruleset in multidimensional tree which drastically reduces the number of rules that need to be inspected until you find the final action on the packet.

I assume you have at least basic experience with the nftables configuration.

Linux Security Networking

How nftables log to external file

Logging traffic blocked by the nftables or iptables firewall rules is necessary for debugging the firewall rules and to be alerted to local software problems. Any packet matching a rule can be logged by using -j LOG target for iptables or log statement for nftables. Logging packet has no effect on the packet's disposition, however. The packet must match an accept or drop rule.

Linux Security Networking

How to Enable Full Disk Encryption with encrypted boot, root partition and ramdisk in Debian - Ubuntu Linux

This is a tutorial on how to get a step-by-step installation of Debian on a fully encrypted disk. We encrypt everything, including the kernel and the initialization ramdisk. Without a password, the thief will not even blow.

Security Debian Linux