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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 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 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.