Name:O365 Mailbox Email Forwarding Enabled id:0b6bc75c-05d1-4101-9fc3-97e706168f24 version:3 date:2024-09-30 author:Patrick Bareiss, Mauricio Velazco, Splunk status:production type:TTP Description:The following analytic identifies instances where email forwarding has been enabled on mailboxes within an Office 365 environment. It detects this activity by monitoring the Set-Mailbox operation within the o365_management_activity logs, specifically looking for changes to the ForwardingAddress or ForwardingSmtpAddress parameters. This activity is significant as unauthorized email forwarding can lead to data exfiltration and unauthorized access to sensitive information. If confirmed malicious, attackers could intercept and redirect emails, potentially compromising confidential communications and leading to data breaches. Data_source:
search:`o365_management_activity` Operation=Set-Mailbox | eval match1=mvfind('Parameters{}.Name', "ForwardingAddress") | eval match2=mvfind('Parameters{}.Name', "ForwardingSmtpAddress") | where match1>= 0 OR match2>= 0 | eval ForwardTo=coalesce(ForwardingAddress, ForwardingSmtpAddress) | search ForwardTo!="" | rename user_id as user | stats count earliest(_time) as firstTime latest(_time) as lastTime values(ForwardTo) as ForwardTo by user ObjectId |`security_content_ctime(firstTime)` |`security_content_ctime(lastTime)` | `o365_mailbox_email_forwarding_enabled_filter`
how_to_implement:You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. known_false_positives:Email forwarding may be configured for legitimate purposes, filter as needed. References: -https://attack.mitre.org/techniques/T1114/003/ -https://learn.microsoft.com/en-us/exchange/recipients/user-mailboxes/email-forwarding?view=exchserver-2019 drilldown_searches: name:'View the detection results for - "$user$"' search:'%original_detection_search% | search user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Office 365 Collection Techniques' asset_type:O365 Tenant confidence:60 impact:70 message:Email forwarding configured by $user$ on mailbox $ObjectId$ mitre_attack_id: - 'T1114' - 'T1114.003' observable: name:'user' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Operation' - 'Parameters{}.Name' - 'src_user' - 'DeliverToMailboxAndForward' - 'ObjectId' risk_score:42 security_domain:threat
