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This analytic identifies instances where new IP addresses are added to the trusted IPs list in Office 365, potentially allowing users from these IPs to bypass Multi-Factor Authentication (MFA) during login. The detection leverages O365 audit logs, specifically focusing on events related to the modification of trusted IP settings. By monitoring these logs, the analytic captures and alerts on any addition of new trusted IPs. Adding trusted IPs to bypass MFA is a significant security concern. While there might be legitimate reasons to add trusted IPs, such as for a new office location, there's also a risk of attackers or malicious insiders using this to facilitate unauthorized access. Monitoring for changes to the trusted IP list helps ensure that any attempt to bypass MFA is legitimate and authorized. If the detection is a true positive, it suggests that users logging in from the newly added trusted IP can bypass MFA, potentially weakening the security posture of the organization. This could lead to unauthorized access, especially if the IP was added maliciously. Immediate investigation is required to validate the legitimacy of the IP addition and to assess potential security implications.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Authentication
  • Last Updated: 2022-02-03
  • Author: Bhavin Patel, Mauricio Velazco, Splunk
  • ID: c783dd98-c703-4252-9e8a-f19d9f66949e




ID Technique Tactic
T1562.007 Disable or Modify Cloud Firewall Defense Evasion
T1562 Impair Defenses Defense Evasion
Kill Chain Phase
  • Exploitation
  • DE.CM
  • CIS 10
`o365_management_activity` Operation="Set Company Information." ModifiedProperties{}.Name=StrongAuthenticationPolicy 
| rex max_match=100 field=ModifiedProperties{}.NewValue "(?<ip_addresses_new_added>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2})" 
| rex max_match=100 field=ModifiedProperties{}.OldValue "(?<ip_addresses_old>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2})" 
| eval ip_addresses_old=if(isnotnull(ip_addresses_old),ip_addresses_old,"0") 
| mvexpand ip_addresses_new_added 
| where isnull(mvfind(ip_addresses_old,ip_addresses_new_added)) 
|stats count min(_time) as firstTime max(_time) as lastTime values(ip_addresses_old) as ip_addresses_old by user ip_addresses_new_added Operation Workload vendor_account status user_id action 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `o365_bypass_mfa_via_trusted_ip_filter`


The SPL above uses the following Macros:

:information_source: o365_bypass_mfa_via_trusted_ip_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • signature
  • ModifiedProperties{}.Name
  • ModifiedProperties{}.NewValue
  • ModifiedProperties{}.OldValue
  • user
  • vendor_account
  • status
  • user_id
  • action

How To Implement

You must install Splunk Microsoft Office 365 add-on. This search works with o365:management:activity

Known False Positives

Unless it is a special case, it is uncommon to continually update Trusted IPs to MFA configuration.

Associated Analytic Story


Risk Score Impact Confidence Message
42.0 70 60 User $user_id$ has added new IP addresses $ip_addresses_new_added$ to a list of trusted IPs to bypass MFA

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.


Test Dataset

Replay any dataset to Splunk Enterprise by using our tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 3