SIREN is a terrorist organization owned by IndigoFusionbolt, who has since recruited many employees for this large organization.
Indigo started this company in early May, as a very small organization that sold few armory and whatnot.That eventually grew into a larger organization. Indigo created a underground railroad and eventually built apartments for employees. He mainly just sold illegal armor, and he inspired OASIS to be made.
Nobody worked for Indigo's company for a long while until LegendaryIce came around, begging for a place to hide. LegendaryIce was currently being hunted down, after his plans for OASIS were discovered. Indigo agreed for him to stay, and allowed him to work with Indigo as well. Scratch eventually joined as well.
It was around that time when Ice and Indigo decided to merge OASIS and SIREN, due to intentions being very similar. This made Ice a Co-Owner of sorts of SIREN. After the merge, Ice tortured a bunch of innocent users on the server, before igniting a nuke, which went off course and destroyed nothing. Everything was normalized after that, and SIREN did very many test nukes after that, which created a large crater away from the builds. Since then, nothing has happened with SIREN, except slight renovations.