↳ Source GitHubRègle analytiqueLow

New UserAgent observed in last 24 hours

Description

'Identifies new UserAgents observed in the last 24 hours versus the previous 14 days. This detection extracts words from user agents to build the baseline and determine rareity rather than perform a direct comparison. This avoids FPs caused by version numbers and other high entropy user agent components. These new UserAgents could be benign. However, in normally stable environments, these new UserAgents could provide a starting point for investigating malicious activity. Note: W3CIISLog can be noisy depending on the environment, however OfficeActivity and AWSCloudTrail are usually stable with low numbers of detections.'
Type de règle
Scheduled
Version
1.0.5
Statut déclaré
Available
Fréquence
1d
Période analysée
14d
Déclenchement
gt 0

Couverture MITRE déclarée

Sources déclarées

Métadonnées du fichier source. Aucune dépendance déduite du KQL.

Connecteurs

Types de données

Requête KQL

Requête originale, sans modification.

let starttime = 14d;
let endtime = 1d;
let UserAgentAll =
(union isfuzzy=true
(OfficeActivity
| where TimeGenerated >= ago(starttime)
| where isnotempty(UserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = ClientIP, Account = UserId, Type, RecordType, Operation
),
(
W3CIISLog
| where TimeGenerated >= ago(starttime)
| where isnotempty(csUserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent = csUserAgent, SourceIP = cIP, Account = csUserName, Type, sSiteName, csMethod, csUriStem
),
(
AWSCloudTrail
| where TimeGenerated >= ago(starttime)
| where isnotempty(UserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = SourceIpAddress, Account = UserIdentityUserName, Type, EventSource, EventName
))
// remove wordSize blocks of non-numeric hex characters prior to word extraction
| extend UserAgentNoHexAlphas = replace("([A-Fa-f]{4,})", "x", UserAgent)
// once blocks of hex chars are removed, extract wordSize blocks of a-z
| extend Tokens = extract_all("([A-Za-z]{4,})", UserAgentNoHexAlphas)
// concatenate extracted words to create a summarized user agent for baseline and comparison
| extend NormalizedUserAgent = strcat_array(Tokens, "|")
| project-away UserAgentNoHexAlphas, Tokens;
UserAgentAll
| where StartTime >= ago(endtime)
| summarize StartTime = min(StartTime), EndTime = max(EndTime), count() by UserAgent, NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
| join kind=leftanti
(
UserAgentAll
| where StartTime < ago(endtime)
| summarize by NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
)
on NormalizedUserAgent
| extend timestamp = StartTime
| extend Name = tostring(split(Account, '@', 0)[0]), UPNSuffix = tostring(split(Account, '@', 1)[0])

Entités déclarées

AccountIP

Contenus associés

Liens établis à partir des identifiants déclarés et des manifests des solutions.

Traçabilité de la source

GitHub

Les valeurs affichées proviennent des fichiers du dépôt Azure/Azure-Sentinel. Elles décrivent le modèle publié, pas la configuration de votre workspace.

Identifiant source
b725d62c-eb77-42ff-96f6-bdc6745fc6e0
Autres fichiers source 3Solutions/Network Threat Protection Essentials/Analytic Rules/NewUserAgentLast24h.yamlsource ↗Detections/MultipleDataSources/NewUserAgentLast24h.yamlmigration-note ↗Solutions/Network Threat Protection Essentials/Data/Solution_NetworkThreatDetection.jsonsolution-membership ↗
GSTEP / SUIVI DU CATALOGUE

Ajouté au catalogue : 16 sept. 2026 · 05:49 UTC
Dernier changement observé : 16 sept. 2026 · 05:49 UTC

Dates de synchronisation GSTEP, distinctes des dates de publication du contenu source.