DMARC - Domain-based Message Authentication, Reporting and Conformance What is DMARC DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication method that verifies a message came from a legitimate sender. DMARC is an open standard for email authentication that helps to prevent fraudsters from forging (spoofing) your domain. DMARC checks that the From field matches the domain in DKIM and SPF authentication checks. DMARC also tells email servers how to handle messages that fail these checks and allows recipients to receive reports on emails that fail authentication. 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
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
Test IMAP with telnet IMAP connection theory The first thing any client needs to do is to make a connection to the remote imap server on a specific port. These ports can vary, but default port for plaintext imap service is 143 , and for encrypted (SSL/TLS) imap service is default port 993 . You can use for plaintext imap connection a telnet utility, or for encrypted imap service you can use openssl s_client command. Networking Linux
Arpwatch - monitor mac addresses change Arpwatch Arpwatch is an open source computer software program that helps you to monitor Ethernet traffic activity (like Changing IP and MAC Addresses) on your network and maintains a database of ethernet/ip address pairings. It produces a log of noticed pairing of IP and MAC addresses information along with a timestamps, so you can carefully watch when the pairing activity appeared on the network. It also has the option to send reports via email to an network administrator when a pairing added or changed. Networking Linux Security
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
ProFTPd Server with virtual users and in SFTP mode How to configure proftpd server with virtual users and with sftp mode. Debian Linux Networking Security
Rewrite uri to lowercase in nginx and apache webserver We want make our uri case insensitive. What it is? When I call uri like https://mybluelinux.com/INdex.html, so such uri will be first rewrite to all lowercase chars like https://mybluelinux.com/index.html. Debian Linux Networking Web Servers
