Office365: Abnormal Logon Detected

Rule ID

PH_RULE_O365_AbnormalLogonDetected

Default Status

Enabled

Description

An Office 365 logon from this user was found to be abnormal based on historic baselines

Severity

MITRE ATT&CK® Tactics

Resource Development

Resource Development consists of techniques that involve adversaries creating, purchasing, or compromising/stealing resources that can be used to support targeting. Such resources include infrastructure, accounts, or capabilities. These resources can be leveraged by the adversary to aid in other phases of the adversary lifecycle, such as using purchased domains to support Command and Control, email accounts for phishing as a part of Initial Access, or stealing code signing certificates to help with Defense Evasion.

https://attack.mitre.org/tactics/TA0042

MITRE ATT&CK® Techniques

T1586.002

Compromise Accounts: Email Accounts

Before compromising a victim, adversaries may compromise email accounts that can be used during targeting. Adversaries can use compromised email accounts to further their operations, such as leveraging them to conduct Phishing. Utilizing an existing persona with a compromised email account may engender a level of trust in a potential victim if they have a relationship, or knowledge of, the compromised persona. Compromised email accounts can also be used in the acquisition of infrastructure

https://attack.mitre.org/techniques/T1586/002

Impacts

Network

Data Source

Office 365 via Management Activity API

Detection

Correlation

Remediation Guidance

Confirm why the user is logging in under suspicious circumstances. Investigate time, source, source country, user agent, method, and so on and confirm that user was intended to login via these methods.

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.

abnormal_logon

SubPattern Definitions

SubPattern Name: abnormal_logon

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

eventType = "MS_OFFICE365_abnormal_o365_logon"

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID

user,srcIpAddr

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

 srcIpAddr=abnormal_logon.srcIpAddr,
user=abnormal_logon.user

FortiSIEM Rules