A rule is generating hundreds of alerts a day. How do you tune it without creating a blind spot?

Analyze the noise before you touch the rule. Group the alerts by host, user, process and command line to find which few sources produce most of the volume, then write narrow exclusions keyed to durable attributes such as a signed binary path plus a specific parent process, not a broad wildcard. Keep the suppressed events searchable, set an expiry review, and document the residual risk you accepted.

First I pull thirty days of that rule and group the hits. Usually eighty percent comes from three sources. On one job a certutil rule was drowning us, and it turned out to be a software deployment agent calling certutil to check a certificate chain on every install. My exclusion was not certutil. It was that specific parent process, from that install path, running as the deployment service account. Anything else calling certutil still alerted. I also kept the events flowing into the data lake with alerting off, so if we needed to hunt across them later the history was there. Then I put a ninety day review on the exclusion and wrote a line in the change record saying what an attacker would need to control in order to abuse it, which here meant compromising the deployment server, and we already had separate monitoring on that box. Volume went from roughly four hundred a day to under ten and we did not lose the technique.