We strongly believe that only combination of deep, low level defensive and offensive security skills can guarantee secure and successful deployments.

Our mission

At Defensive Security we focus on teaching you best practices in securing your Open Source infrastructures. Almost 15 years of experience, best ever training flow and high passion level guarantee you the best in the market of IT Security Education & Solution Services.

Why us

Our Certificates


44CON 2019/2020

44CON is an Information Security Conference & Training conference taking place in London. It is designed to provide something for the technical and business Information Security professionals.

Copenhagen Cybercrime Conference 2019

The Cyber Security Conference that focuses on sharing knowledge rather than sales pitches. Attending this conference enables participants to learn about cyber security’s most important current issues, meet and network with international and regional cybersecurity practitioners and focus on original ideas drawn from real-world situations.


SECURE Conference is one of the most important IT Security events in the calendar of polish *Cyber Security* conferences. As it appears on the web page, it's organized by NASK and CERT Polska operating within the structure of NASK

Infosec in the City 2019

Infosec in the City, Singapore (IIC-SG) is a premier techno-centric cybersecurity event that brings top cybersecurity leaders and experts from both the East and the West together to share and discuss deep technical topics and insights, and build the next-generation cybersecurity capabilities and capacity around the globe.

Hack In The Box 2018/2019/2020

Hack In The Box Security Conference is an annual must attend event in the calendars of security researchers and professionals around the world. Held annually in Kuala Lumpur, Malaysia and Amsterdam in The Netherlands, HITBSecConf is a platform for the discussion and dissemination of next generation computer security issues.

Black Hat USA 2019

Black Hat is the most technical and relevant information security event series in the world. For more than 20 years, Black Hat Briefings have provided attendees with the very latest in information security research, development, and trends in a strictly vendor-neutral environment.

Brucon 2017/2018

BruCON is an annual security and hacker(*) conference organized in Belgium, providing two days of an interesting atmosphere for open discussions of critical infosec issues, privacy, information technology and its cultural/technical implications on society.

Exatel Security Days 2017

One of the best commercial IT Security Conference in Poland. In 2017 I presented: "May the data stay with U! - Network Data Exfiltration Techniques."

Confidence 2016

The most famous IT Security Conference in Poland since 2005. In 2016 I had a speak about "Honey(pot) flavored hunt for cyber enemy". CONFidence gathers 500 attendees each year.

PLNOG 2016

The biggest Polish Network Operators Group Conference. In 2016 I had a presentation "Yo, yo! It's us, packets! Catch us if you can."

OWASP Poland

Polish chapter of Open Web Application Security Project - non-profit organization focused on improving the security of software. In 2013 I was speaking about Web Application Firewall - "Mod security - does your WAF can do it?"

Open Source Day

The biggest Open Source Conference in Poland as well as in EMEA region. In years 2008-2014 I was going deeply into SELinux, Linux Hardening, Web Application Security and new features in Red Hat Enterprise Linux.

Atmosphere 2014

Atmosphere 2014 – Performance and Scalability (500+) - Warsaw: “Scalable and under control - open cloud architecture considering security standards.”

Why us

  • Almost 15 years of experience in IT security technology supporting the largest companies and institutions for implementation, consulting and technical training
  • 11 years of experience in teaching and transferring technical knowledge and experience (number of trained persons: 500+, the average evaluation on a 1-5 scale: 4.9.
  • IT Security Architect with pentester’s passion and recognized expert of enterprise Open Source solutions.
  • Providing web application and infrastructure penetration tests
  • Specializing in Linux/OS hardening and defensive security of web application platforms
  • Known and respected trainer/examiner of Red Hat products in Poland (RHCA, RHCSS, RHCE)
  • The author of many IT Security workshops (In & Out series, Open Source Defensive Security, ModSecurity, FreeIPA, SELinux, Linux Hardening).
  • Speaker at conferences: Secure 2019, Cyber Hagen 2019, Advanced Threat Summit 2019, Confidence 2016 (“Honey(pot) flavored hunt for cyber enemy), PLNOG 2016 (“Yoyo! It’s us, packets! Catch us if you can”), NGSEC 2016 (“Many security layers for many defensive opportunities”), Open Source Day 2010/2011/2012/2013/2014, SysDay 2008 (“SELinux vs exploits”), Confitura 2014 (“Detection and elimination of threats in real-time - OWASP Appsensor in action.”), Red Hat Roadshow 2014, OWASP Chapter Poland 2015(“Does your WAF can handle it?), ISSA InfoTrams 2015, BIN Gigacon 2015(“Mapping pentester's knowledge for the need to protect a critical IT infrastructure”).
  • An associate member of ISSA and OWASP Poland Poland.

If you need to get deep and broad knowledge in the scope of Defensive Security using Open Source software then don't hesitate and just grab for it - definitely worth to attend and meet Leszek in person and his experience during 3 days long comprehensive technical training. "

Wojciech Dworakowski CEO at SecuRing

Our clients include