If you are building or improving a SIEM, start with the logs before you start with the rules. A detection rule is a query over stored events. It works only when the SIEM receives the events the rule expects, parses the fields analysts need, and keeps the data long enough for an investigation.

In a SIEM review, check the data requirement for each detection before judging the rule library. The event must exist, the relevant fields must parse cleanly, and the data must remain searchable long enough for analysts to use it. A good rule can still fail when the required source is absent or poorly parsed.

Use the nine categories below as a review checklist. For each one, decide whether the source is present, whether analysts can join it to identity and asset context, and whether retention is long enough to answer incident questions after the first alert appears.