This special issue of the Australian Journal of Multi-Discplinary Engineering arose as an outcome of the 'Engineering a Secure Australia' project run by Engineers Australia, which is a two year activity to enhance homeland security by engineering security into the nation's infrastructure, information technology and elements of the built environment. This issue includes the following papers 'Risk assessment as a decision-making tool to mitigate blast damage to built infrastructure'; 'Safeguarding transport networks: the assessment of network vulnerability'; 'Security by design - the new challenges of terrorism to airport terminals'; 'The threat of surprise'; 'Design considerations for protection of building facades from bomb blasts'; 'Analysis of blast loads on buildings'; 'Blast-resilient design for buildings structures'; 'Retrofitting existing masonry buildings to resist explosions'; 'Counter terrorism & critical infrastructure protection - managing them with GIS technologies'; 'Critical infrastructure in speech and sound processing and its effect on the security of Australia'; and 'Securing critical information network infrastructures from attacks'.