The process of radicalisation can be different for each person but in many cases happens over a long period of time. Radicalisers may use the internet (social media, online gaming) or interest groups, to befriend and begin to indoctrinate someone towards an ideology or set of beliefs that are extreme and can lead to criminality or in some cases, terrorism.
Radicalisers often present extreme ideologies in a way which appeals to the grievances of the individual they are trying to radicalise. These beliefs and ideologies may appear credible at first but during the process of radicalisation usually become increasingly extreme.