About me

For 20 years I’m an aficionado for anything related to internet security and developing secure software. I’m specialized in hacking, IT security research and performing advanced penetration testing. My specialty is breaking IT security and then explaining this in a comprehensible way how I did it.

Before venturing into information security, I was lead software developer at various software companies. I’m an expert at finding security vulnerabilities in websites and infrastructure, and know how my findings relate to business risks, and am able to translate these into a solid business strategy.

I’m primarily interested in security in its broadest incarnation, and more specifically, in investigating security weaknesses. Ever since 1997, I’ve actively studied the hacker scene to gain a better understanding and deeper knowledge of their modus operandi as well as frame of mind; thus enabling me to detect, to resolve and to prevent security holes in IT systems and business processes.

Since 2005, I’ve performed professional security tests and have now completed more than 650 security assessments. I’ve also developed over one hundred websites with PHP, MySQL, Apache and Linux as software stack.


If you’re a journalist and need some pictures of me, I’ve collected some for you here.

About Sijmen Ruwhof

Independent IT Security Researcher / Ethical Hacker
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