Luka Gerzic

A place to offload stuff from my brain, from time to time. Usually only IT stuff.

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Tracking your privacy

3.88 billion people are online as of June 2017. Out of 7.51 billion people living on our planet, 51.7% is using Internet. Everything is connected. Everything will be connected. Internet is awesome, we all learn, create and share information over the Internet. The time we all spend online, especially young generation is constantly increasing. This is the true power of Internet.

But as Internet opened to all of us, we also opened us to it. To be able to utilize this “free” Internet of ours, we have a price to pay, and that price is our privacy. Our privacy is now our currency to the “free” digital trove of information on the Internet that we pay, without us even realizing it.

We leave all our private information on the Internet: birthdays, places of residence, phone numbers, email addresses, social security numbers, credit cards, GPS coordinates of our movement, our preferences and...

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33c3 Packing

This year, for 33c3 I am packing lite. Some friends asked what gear I will bring to event, and instead of repeating myself, I have decided to make small blog post about it. Idea is to pack everything with one backpack for easy carry.


1) GORUCK GR1 backpack
2) GORUCK wire dopp
3) Lenovo T440s notebook
4) Mac Book Pro 13" Retina
5) GORUCK field pocket (cables, chargers etc.)
6) Lenovo extra batteries for Lenovo T440s
7) Tenergy 16k battery pack
8) Zendure battery pack
9) Box for various antennas
10) Hard padded case for 3.5" HDD’s or other items
11) Notepad
12) Headphones
13) USB lamp
14) Lock picks
15) Thermal USB cam
16) Nalgene 1L bottle
17) TP-LINK M5350 Router
18) TP-LINK 3020
19) Motorola c118
20) Nokia 6210
21) Nexus 5
22) Baofeng GT3
23) Surefire
24) Letherman
25) USRP B200
26) 12V inverter
27) Netgear GS105E+
28) Alfa Wifi USB dongles
29) Ubertooth
30) DVB SDR USB dongle

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DEAUTH_LEAVING or Reason3 or fucking CRDA

Before you start reading a warning, this blog entry is rant. End of warning.

You might get frustrated by somewhat irregular behavior of your WiFi adapters (especially if you travel a lot to different regions), with errors like these:

    kernel: [ 1549.345884] alfa0: deauthenticating from XX:XX:XX:XX:XX:XX by local choice (Reason: 3=DEAUTH_LEAVING)

    kernel: [ 3330.004070] wlan0: deauthenticated from XX:XX:XX:XX:XX:XX (Reason: 3=DEAUTH_LEAVING)

And then you start investigating and banging your head on the table what’s the fucking reason for your beloved WiFi adapter to behave and de-auth out of your so much needed AP.

Well you can thank the regulations and restrictions set for different countries. As per

“Every card sold was certified to work in a particular regulatory environment (that being set of channels, maximum allowed power, other...

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Custom made versatile autonomous MiTM WiFi box v1.0

Recently I have published a photo of this box on twitter and couple of people asked if I can share more details on how I have build it. I did plan to do it, but never got to actually spend some time writing about it. So this would be long overdue blog post on building and assembling of MiTM WiFi box that I was using during some penetration testing scenario’s in the past.


Usual disclaimer: Do not use such device(s) without written consent of your target(s). In some countries this is illegal and you could bare serious legal consequences if you use it without permission.

Tool requirements

To build this box, you will most likely need these tools:

  • A drill
  • 5 or 6mm wood/metal drill bit
  • Open end spanner - size 8
  • Pliers
  • Scalpel
  • Zip ties

The BOX selection

While searching for box that could be used for this project, there where some requirements that I wanted to acquire, as this was...

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How secure is .rs?

In 2014, we did a report titled “National domain security analysis” (pdf) under RNIDS (Serbian National Internet Domain Registry) sponsorship. This study was then presented (same year) on debate panel “3u1” during “European Cyber Security Month”, organised by ENISA, the European Union Agency for Network and Information Security and RNIDS.

Participants, general public and media showed broad interest in this study and it was well received by media at that time. Blic, B92, Live TV, IT Svet, PC Press, Biznis i Finansije, Personal Mag, Dnevnik, etc.

This resulted in more panels, presentations and improvements over original report, mainly at ETF (Faculty of Electrical Engineering), FON (Faculty of Organizational Sciences), Faculty of Security Studies and others.

Our hope was that this 2014 report and analysis will serve as foundation for business and technical decision makers. As the...

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Ettus Research USRP B200/B210 simple case

Hi there. If you are into SDR and out looking for signals, you have probably heard about Ettus Research products.

In case you have bought B200 or B210 product you know that these will be delivered without any case/box. Since this product is a bit expensive and you for sure want to have some kind of protection, here is idea you could use for your device.

I have heard that some people had luck to have someone who can build special purpose case(s) from aluminum, or have patience to wait for special China delivery (for months), but for those who are in no luck, we can simply use some 5mm Acrylic Glass as it’s very common, cheap, easy to cut, engrave and provides fair protection for packing and traveling.

First, get one of these vector files I have created for cutting and if you like engraving of Acrylic Glass sheets. You can give these to anyone who has Laser engraving services. Here...

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