An "Multiple User Accounts Were Disabled" investigation came back with one
entity — the actor — while the layout stayed nearly empty. Four separate
reasons, and the last one is why the first three keep recurring.
evidences was an OBJECT, not an array. JSONata returns a bare object when the
path yields one item, so the key had one shape on an investigation with a
single alert and another with two. Bracketed to force an array.
Only the actor was mapped. An ad_admin rule names who acted AND who it was
done to, and on this alert the disabled accounts are the point of it. Target
account, target user and both domains now map to the OCSF Target User group,
the actor to Actor — the distinction that lets the sentence be read in one
line.
The domain controller was nowhere. A Windows event puts it in
source_json.computerName and nowhere else, and source_json was skipped whole
because the Azure AD one runs to kilobytes. Its top-level SCALARS are now
read — bounded, and where computerName, osVersion and callerIpAddress live —
while its nested part stays skipped.
source_asset was the string "unknown". Mapped as-is it becomes an asset named
"unknown" in the entity index, shared by every incident that had no asset: a
pivot that groups things by the absence of a fact. Placeholders are dropped,
and a key whose value cleans away to nothing is removed rather than kept
empty, since "" is not nil and would still be written to its OCSF field.
Five entities now, from one: both accounts, both display names, the DC.
And the reason this kept happening. The layout builder's field picker is a
closed <select> over the OCSF catalogue in web/src/lib/ocsf.ts, so a path absent
from it cannot be placed on a layout at all — which is what `detection` and
`evidence` are, and what every unanticipated key will be. Mapping each one to a
real OCSF field is right where a field exists, but rule_keys_of_interest is an
open vocabulary: four spellings turned up in as many days.
So the whole of it is also rendered as a Markdown table into
custom:rapid7_summary — keys of interest first, since the rule itself says
those are what matter, then the evidence fields. Declare a custom field of type
markdown with that name, put it on the layout, and a new rule type is readable
the day it appears instead of after another mapping round.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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