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Detection rules › Kusto

Suspicious TGT Request with a DC Account

Author
Cyb3rMonk
Source
github.com/Cyb3r-Monk/Threat-Hunting-and-Detection

Below query detects TGT requests from a DC account with an IP that doesn't belong to a DC. It detect PetitPotam and any other attacks that uses a stolen DC certificate/account to perform operations.
If you make it a detection rule, take ingestion delay into account.

MITRE ATT&CK coverage

TacticTechniques
Credential AccessNo specific technique

Event coverage

ProviderEventTitle
Security-AuditingEvent ID 4768A Kerberos authentication ticket (TGT) was requested.

Rule body kusto

// Author       : Cyb3rMonk(https://twitter.com/Cyb3rMonk, https://mergene.medium.com)
//
// Link to original post:
// https://posts.bluraven.io/detecting-petitpotam-and-other-domain-controller-account-takeovers-d3364bd9ee0a
//
// Description  : This query detects if a computer account of a Domain Controller is stolen and used from a Non-DC device. 
//                computer account of a DC can bu used to obtain a TGT.
//
// Query parameters:
//
// list of DCs
let DCs = dynamic(["yourdc1.yourdomain.local"]);
// list of DC IPs
let DC_IPs = dynamic(["IP of the DCs including IPv6 addresses"]);
//
SecurityEvent
| where EventID == 4768
| where Computer in~ (DCs)
| where TargetUserName endswith "$"
| where DCs has replace_string(TargetUserName,"$","")
| where IpAddress <> "::1"
| extend IpAddress = replace_string(IpAddress, "::ffff:", "")
| where IpAddress !in (DC_IPs)
| project-reorder Computer, TargetUserName, IpAddress

Stages and Predicates

Parameters

let DCs = dynamic(["yourdc1.yourdomain.local"]);
let DC_IPs = dynamic(["IP of the DCs including IPv6 addresses"]);

Stage 1: source

SecurityEvent

Stage 2: where

| where EventID == 4768

Stage 3: where

| where Computer in~ (DCs)

Stage 4: where

| where TargetUserName endswith "$"

Stage 5: where

| where DCs has replace_string(TargetUserName,"$","")

Stage 6: where

| where IpAddress <> "::1"

Stage 7: extend

| extend IpAddress = replace_string(IpAddress, "::ffff:", "")

Stage 8: where

| where IpAddress !in (DC_IPs)

Stage 9: project-reorder

| project-reorder Computer, TargetUserName, IpAddress

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
IpAddresseqDC_IPs

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.

FieldKindValues
Computerin
  • DCs
EventIDeq
  • 4768 transforms: cased corpus 13 (splunk 11, kusto 2)
IpAddressne
  • ::1 transforms: cased
TargetUserNameends_with
  • $ corpus 7 (sigma 5, kusto 2)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

FieldSource
IpAddressextend