Best Practices on Email Protection: SPF, DKIM and DMARC

Once we installed Zimbra Collaboration, we need to be aware of some additional configurations that will allow us to send emails to other Email systems with an improve Security, such Gmail, Hotmail, Yahoo!, etc. This Wiki article will show the different Email Protection resources that exists, depends of the volume of sent email, will be better to implement only one, or two, or maybe all of them, depends.

SPF
Sender Policy Framework (SPF) is an email validation system, designed to prevent unwanted emails using a spoofing system. To check this common security problem, SPF going to verify the source IP of the email and compare it with a DNS TXT record with a SPF content. 

Where needs to be configured?
SPF needs to be configured in the Public DNS Continue reading “Best Practices on Email Protection: SPF, DKIM and DMARC” »

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How to start Google Chrome in Incognito Mode default

  1. Place a Google Chrome shortcut on the desktop (or any other desired location).
  2. Rename the shortcut to any convenient name like – Private Chrome.
  3. Right click on the shortcut and select “˜Properties’.
  4. On the “˜Target’ field add an –incognito to the end of program path. (Note: Make sure there is a space between the last apostrophe and the dash).
  5. Your incognito browser is now ready for launch. If you select “˜New Window’ from settings, you will get a normal non-incognito chrome window.

Continue reading “How to start Google Chrome in Incognito Mode default” »

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Telecom is at a crossroad. The telecom business is starting to fail.

Ericsson and Nokia, the number two and three suppliers, have their debt rated as junk. Verizon is selling, what should have been its future, their cloud business, to IBM. AT&T is loosing wireless subscribers every quarter. Telefonica, the innovation leader, is scaling back its IoT Smart City business. Telecom as an industry is getting to a crossroad. Whatever road they take will decide their future. The closest resemblance is the moment IBM discovered that PCs and servers were a commodity. They decided to become a services and software company. Competitors of them did not. These competitors might not be around for many more years. Communication has been commoditised. Calls and SMSes are dead. Long live WhatsApp and others! Even Twilio, the SMS and call disruptor, is having problems. Continue reading “Telecom is at a crossroad. The telecom business is starting to fail.” »

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ip_conntrack table full, dropping packet

Last week, I found myself with a server under low load, but it couldn’t make or receive network connections. When I ran dmesg, I found the following line repeating over and over:

ip_conntrack: table full, dropping packet
I’d seen this message before, but I headed over to Red Hat’s site for more details. It turns out that the server was running iptables, but it was under a very heavy load and also handling a high volume of network connections. Generally, the ip_conntrack_max is set to the total MB of RAM installed multiplied by 16. However, this server had 4GB of RAM, but ip_conntrack_max was set to 65536:

# cat /proc/sys/net/ipv4/ip_conntrack_max
65536

I logged into another server with 1GB of RAM (RHES 5, 32-bit) and another with 2GB of RAM (RHES 4, 64-bit), and both had ip_conntrack_max set to 65536. I’m not sure if this is a known Red Hat issue, or if it’s just set to a standard value out of the box. Continue reading “ip_conntrack table full, dropping packet” »

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ওমরাহর নিয়ম

১. ওমরাহর ইহরাম (ফরজ)
· পরিষ্কার-পরিচ্ছন্নতা সেরে গোসল বা অজু করে নিতে হবে
· মিকাত অতিক্রমের আগেই সেলাইবিহীন একটি সাদা কাপড় পরিধান করুন, অন্যটি গায়ে জড়িয়ে নিয়ে ইহরামের নিয়তে দুই রাকাত নামাজ পড়ে নিন
· শুধু ওমরাহর নিয়ত করে এক বা তিনবার তালবিয়া পড়ে নিন Continue reading “ওমরাহর নিয়ম” »

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Understanding RAID

I always try to share what I learn, and a few days back was looking for a single page short cut summary notes on various RAID level for the storage units. Found this article quite resourceful and exactly a single paged document that I was looking for.

Now sharing the content for the readers. Enjoy!

RAID 0 (STRIPE)

raid-0 (1)RAID 0 splits data across drives, resulting in higher data throughput. The performance of this configuration is extremely high, but a loss of any drive in the array will result in data loss. This level is commonly referred to as striping.

  • Minimum number of drives required: 2
  • Performance: High
  • Redundancy: Low
  • Efficiency: High

Continue reading “Understanding RAID” »

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GoodReads: How to use Docker in a practical way (part 1 – Introduction)

Part 1: Introduction to the terminology

Preface

It is not an uncommon situation, for early adopters of newly introduced concepts and technologies, to be totally confused when these can fundamentally change the ways of developing and delivering services. Especially when everybody talks about something like Docker, and how awesome and game changing it is. This confusion happens when we try things early on and rushing straight to testing them without grasping the whole concept and background of this newly introduced technology.

This is why you may have abandoned the whole trend of Linux containers, or because you read some controversial article from yea sayers and naysayers. In this first part, of a series of articles, we will try our best to clear things up and put everything on the right perspective for any developer, sysadmins, Q/A engineers or even enthusiasts who just need the right inspiration to use Linux containers and solve their special IT problems.
We will start from the beginning, with some necessary description of the historical events and concepts and then I will showcase how we can start working with Docker containers. This way, you will be able to understand “what led to the creation of containers”, “what are the building blocks” and “how do they work”. Continue reading “GoodReads: How to use Docker in a practical way (part 1 – Introduction)” »

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Prophet Muhammad’s Last Sermon

Read it first in Bangla while was a school student, likely to be in my religion classes. Thought might be useful to other.

Prophet Muhammad’s final sermon was delivered during the Hajj of the year 632 C.E., the ninth day of Dhul Hijjah, the 12th month of the lunar year, at Arafat, the most blessed day of the year. There were countless Muslims present with the Prophet during his last pilgrimage when he delivered his last Sermon. Continue reading “Prophet Muhammad’s Last Sermon” »

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Mustafizur stars in landmark series win- Bangladesh v India, 2nd ODI, Mirpur

216075Bangladesh 200 for 4 (Shakib 51*, Ashwin 1-32) beat India 200 in 45 overs (Dhawan 53, Mustafizur 6-43) by six wickets (D/L method)

Mustafizur Rahman was the hero in Mirpur again, (off)cutting through India’s batting with a six-wicket haul to add to his five-for on ODI debut, and launching Bangladesh to their first ever bilateral series win against India. Mustafizur’s 6 for 43, the second best figures by a Bangladesh bowler in ODIs, skittled India for 200, before Shakib Al Hasan steered the chase with a busy fifty, his second on the trot.

With this six-wicket win, Bangladesh also cemented their place in the 2017 Champions Trophy. An overjoyed Mashrafe Mortaza, who has been a part of each of Bangladesh’s five victories against India, toasted his team’s “big achievement”.

Why Bangladesh’s target was 200
When the rains came, India were already eight wickets down after 43.5 overs. Because the game was revised to 47 overs per side, India lost out on some batting opportunity, but that loss was minimal as they were already eight down at the time of the interruption. According to the DLS calculations, the batting resources denied to Bangladesh at the start of their innings, compared to what they would have had in a full 50-over innings, was marginally more than the resources India lost out on.

Continue reading “Mustafizur stars in landmark series win- Bangladesh v India, 2nd ODI, Mirpur” »

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Pf vs Iptables- a Great comparative article

I enjoyed reading the following article, though would worth keeping a copy on my blog. Happy Reading-

Today I will be talking a lot about OpenBSD, FreeBSD and other Unix-like operating systems from the Berkeley Software Distribution. I thought that would be appropriate being my first document on Unixmen. I however will also be talking about Linux and Untangle and how they complement Unix based firewalls such as Pfsense.

I would like to explain what I think is the best way to secure a network from hackers and bots and why these techniques work as well as I say they do. I however will not be explaining how, as I will save that for another article. That being said if there is anything in error here please let me know but I am sure you will find nothing in contrast to common theory. I would also like to show you guys some things I like to do and things I think are critical to IT security. Continue reading “Pf vs Iptables- a Great comparative article” »

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