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Network penetration testing, web application security, firewall review, CHECK pen testing, server build review, social engineering..

About Joseph Sheridan

Joseph Sheridan is the founder and Director at ReactionIS, an independent, CESG-approved CHECK pen testing consultancy. He has been involved in IT security and penetration testing for over a decade and has provided security consultancy to some of the most prestigious organisations in the UK. In between pen testing engagements, Joseph carries out vulnerability research and has uncovered important security flaws including remotely exploitable buffer overflows in commonly used software products.


Joseph began his career as a programmer for BAE Systems and then as a researcher in secure operating-systems at the University of Kent before entering the world of commercial pen testing and IT security consulting. Since then, Joseph has delivered penetration testing services and security advice to a large number of high profile government and banking clients, local and central government organisations, retail and investment banks, legal and insurance companies and other FTSE and non-FTSE companies. Joseph started ReactionIS in 2009 and now heads up the team as Lead Consultant and ensures that the highest standards of testing are maintained across all projects.


Joseph is a CHECK Team Leader (since 2008), a CREST Consultant (in both web applications and infrastructure disciplines), and a CISSP (Certified Information Systems Security Professional). He graduated from Nottingham University in 2002 with a first class Computer Science degree and maintains many security clearances including HMG and NATO (please ask for more details).

For further information, read Joseph's consultancy recommendations and details of his research activities including the GIMP ScriptFu buffer overflow vulnerability which now features as one of the Metasploit exploit modules.

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Penetration Testing Services

Firewall reviews, database audits, code reviews, social engineering and more..

Application Security

Ensure your web and mobile apps are safe from attack.

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