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This article explains the most commonly used Email protocols on the internet – POP3, IMAP, and SMTP SMTP 25, 2525 SMTP-SSL/TLS 587,465 IMAP 143 IMAP-SSL/TLS 993 POP3 110 POP3-SSL/TLS 995 587 vs. 465 These port assignments are specified by the Internet Assigned Numbers Authority (IANA): Port 587: [SMTP] Message submission (SMTP-MSA), a service that accepts submission of email from email clients (MUAs). Described in RFC 6409. Port 465: URL Rendezvous Directory for SSM (entirely unrelated to email) Historically, port 465 was initially planned for the SMTPS encryption and authentication “wrapper” over SMTP, but it was quickly deprecated (within months, and over 15 years ago) in favour of STARTTLS over SMTP (RFC 3207). Despite that fact, there are probably many servers that support the deprecated protocol wrapper, primarily to support older clients that implemented SMTPS. Unless you need to support such older clients, SMTPS and its use on port 465 should remain nothing more than a historical footnote. ...

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When you run MySQL commands MySQL, mysqlcheck, mysqdump and psql, psqldump etc; they will pick username & password from this file if you do not provide them as argument (-u and -p). It can save you time. Of course, if you specify username and password explicitly as part of the command’s arguments, they will be used. .pgpass ( for psql client ) test1.net:5432:testdb1:testuser1:testpass1 test2.net:5432:testdb2:testuser2:testpass2

fail2Ban is a very handy tool to prevent a lot of unwanted traffic from consuming bandwidth on your servers. It’s a minimal and relatively simple IDS Type Tool that comes with some predefined filters to automatically lockout potentially dangerous or bandwidth-consuming type attacks. 1. creating a custom filter /etc/fail2ban/filter.d/custom.conf [Definition] badagents = 360Spider|ZmEu|Auto Spider 1.0|zgrab/[0-9]*\.[0-9a-zA-Z]*|Wget\(.*\)|MauiBot.* failregex = ^.+?:\d+ <HOST> -.*"(GET|POST|HEAD).*HTTP.*(?:%(badagents)s)"$ ignoreregex = 2. test the custom filter against a log file using the following command fail2ban-regex /path-to-samples/sample.log /etc/fail2ban/filter.d/custom.conf ...

Logrotate is a system utility that manages the automatic rotation and compression of log files. If log files were not rotated, compressed, and periodically pruned, they could eventually consume all available disk space on a system. Logrotate’s configuration information can generally be found in two places: /etc/logrotate.conf: this file contains some default settings and sets up the rotation for a few logs that are not owned by any system packages. It also uses an include statement to pull in configuration from any file in the /etc/logrotate.d directory. ...