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section tag Enforced, encrypted, self-hosted DNS solution for Android devices

| Pekka Helenius |  July 23, 2021 
Updated:  August 11, 2021 
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Did you know all internet addresses you browse on your Android mobile phone or tablet are resolved by Google DNS servers (,, 2001:4860:4860::8888 and 2001:4860:4860::8844) as plain-text traffic, and due to that, your ISP may also know your browsing or application use habits?

The newest Android versions have feature known as private DNS. However, it accepts and uses only domain names instead of raw IP addresses, so I wouldn't trust the feature too much. Quite obviously you can use VPN. However, you are dependent on an external VPN provider service - and you hardly get useful DNS query logs at all.

So, no use either for built-in private DNS feature or VPN. What then? My answer: use a self-hosted DNS server with encryption support, running on your Android tablet or phone. Enforce every single DNS query by Android applications via that server. How? Keep reading. You need a rooted Android device.

section tag Kerberos-secured network file shares - practical guide for kerberized NFSv4

| Pekka Helenius |  February 12, 2021 
Updated:  November 9, 2021 
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Sharing sensitive data in secure manner is important on many critical network environments, and Kerberos security provides much needed security layer for insecure NFSv4 file sharing. This article focuses on setting up, configuring and testing MIT Kerberos V5 + NFSv4 file sharing on Linux environment.

Unlike many blog articles, I take one step further and explain how to set-up such environment with not just two but four individual Linux computers: Combined Kerberos LDAP back-end and user database server, Kerberos KDC & Administration server, NFSv4 server and NFSv4 client.

section tag HikinGrounds: A website for outdoor people

| Pekka Helenius |  November 27, 2020 
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I recently opened website The website is for people looking for various outdoor activities in multiple parts of the world. Currently, the website is in an early stage of its development cycle.

The website is powered by modern Java back-end technologies: Spring framework and Thymeleaf template engine.

First development phase of took a month, and implements user sign up & access control and a SQL database with nearly 30 tables. Although I heavily focused on back-end development in the first phase, I also use some front-end technologies such as JQuery & Bootstrap to provide necessary UI functionality.

section tag Why does security matter?

| Pekka Helenius |  October 26, 2020 
Updated:  October 29, 2020 
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At the time of writing this post, my home country, Finland, is widely shocked by successful attacks against a private psychiatric center Vastaamo from which a black hat hacker(s) obtained thousands of sensitive patient records by gaining access to an unprotected database server and network infrastructure. And the data is leaked in Tor network in steps, bitcoin payments are demanded, threatening emails are being sent to victims who panic.

section tag OpenNTPD - now with OpenSSL support

| Pekka Helenius |  August 2, 2020 
Updated:  January 21, 2021 
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For a few weeks, I've been working on implementing OpenSSL support and vastly improved configurability to OpenBSD-based NTP daemon OpenNTPD. Both of which I have done now. OpenNTPD is written in C. See the implementation on GitHub - openntpd-openssl.

I run a Linux server infrastructure with time-critical daemons such as Kerberos and Bind9 DNS server. Therefore, I see it's essential to have a local, secure NTP server software.

section tag TinyForest - Self-developed automation system for home

| Pekka Helenius |  April 9, 2020 
Updated:  April 20, 2020 
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Home automation is a large field with many market products available. TinyForest is another home automation system, developed and designed from scratch for various target environments, written in Python 3 and ReactJS. In time writing this article, TinyForest core system is fully functional, and further improvements are planned. It adapts to multi-sensor and multi-device configurations, and can handle everything from irrigration and heating to light controls.

section tag Malicious trojan for Steam installer

| Pekka Helenius |  December 13, 2019 
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Imagine a popular and widely spread Microsoft Windows application you'd like to exploit or create a backdoor for? Problem is: Many applications, such as setup program of Steam gaming platform by Valve Corporation is protected against common tampering or injection attempts.

However, there is a way to add malicious content into such programs. In this post, I demonstrate a simple attack approach and countermeasures which you should remember in any software environment.

section tag SaltStack automation for Android phones & tablets

| Pekka Helenius |  November 19, 2019 
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Do you want to gather data from multiple Android devices remotely at the same time or control the devices? Absolutely possible. Although digital markets have solutions already, I wanted to do the task bit differently with common server management tools: SaltStack.

It turned out to be possible: Android devices can successfully be controlled with SaltStack.

section tag Automating Windows Active Directory deployment

| Pekka Helenius |  October 8, 2019 
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Have you ever wanted to take a cup of coffee while installing Windows Active Directory?

I recently had one this kind of task which is why I decided to give control for semi-automated PowerShell modules & scripts, written from scratch. System administrator should supply parameters for the installation process to use. Otherwise, deployment of the whole AD: fully automated.

section tag Fan Noise Reduction of HP Procurve 2650 Switch

| Pekka Helenius |  September 18, 2019 
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In the earlier post I mentioned noisy fan of my recently bought HP Procurve 2650 L3 Switch. Today, I have a solution to the problem.

Actually, noisy fans seem to be quite common in rack/server room targeted network devices (switches, routers). According to my observations, the problem covers Cisco Catalyst 2960-S switches, as well. This is a major problem if any of these switches are installed at otherwise silent office or school environments.

There are basically two methods to work around the noisy fan problem.

section tag Home Lab - First steps

| Pekka Helenius |  August 31, 2019 
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Home lab? Yes, first steps taken! This has been in my mind for some time. Why? First for learning purposes but it has potential for more in the future. Home network lab is not a same thing than large corporate network with multiple inter-connected sites, but it is a good start, anyway!

Home lab gives me an opportunity to get my hands on real stuff to see a blink of the physical side of network planning, giving more perspective for the whole process rather than only playing with logical (or virtually simulated) network topologies in network simulation software.

section tag Network virtualization with GNS3

| Pekka Helenius |  August 6, 2019 
Updated:  August 15, 2021 
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On a complex networking environments, investing to physical devices before doing a solid planning is almost never a good approach.

Thankfully, there are solutions to this issue. Actually, multiple ones. The keyword for all solutions is virtualization. Why not to simulate and optimize physical network environment as close as you can before investments? And playing with networks, it can be both fun and challenging.

This post covers basic idea of GNS3, an open-source network virtualization solution. In GNS3, simulated networks can, if allowed, access physical networks and vice-versa + you can use real (virtualized) operating systems in addition to router, switch and firewall software.