DiagTrackEoP Default Login Username

Severity: critical
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects the default "UserName" used by the DiagTrackEoP POC

Event coverage

Provider	Event ID	Title
Security-Auditing	4624	An account was successfully logged on.

Stages and Predicates

Stage 1: `selection`

LogonType: 9
TargetOutboundUserName: thisisnotvaliduser

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`LogonType`	eq	`9` corpus 5 (sigma 5)
`TargetOutboundUserName`	eq	`thisisnotvaliduser`

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.

Potential Account Takeover - Mixed Logon Types [elastic] (cross-vendor) (drops 2 filters this rule applies) (first-stage match only; downstream stages may differ)
Potential Account Takeover - Logon from New Source IP [elastic] (cross-vendor) (drops 2 filters this rule applies) (first-stage match only; downstream stages may differ)
Outgoing Logon with New Credentials [sigma] (drops 1 filter this rule applies)