A practical field guide to why a "converted" SIGMA rule so often fires on nothing — or everything. The author walks through field-mapping drift against ECS, the log-source conditions people silently drop during conversion, and the tuning pass that has to happen against your own data before a rule is trustworthy.

Most valuable takeaway: conversion is the first 20% of the work; budget the other 80% for mapping verification and tuning against production telemetry.