IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Suspicious Microsoft 365 Mail Access by ClientAppId
editSuspicious Microsoft 365 Mail Access by ClientAppId
editIdentifies when a Microsoft 365 Mailbox is accessed by a ClientAppId that was observed for the fist time during the last 10 days.
Rule type: new_terms
Rule indices:
- filebeat-*
- logs-o365*
Severity: medium
Risk score: 47
Runs every: 5m
Searches indices from: now-30m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References:
Tags:
- Domain: Cloud
- Data Source: Microsoft 365
- Use Case: Configuration Audit
- Tactic: Initial Access
Version: 107
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
editTriage and analysis
Investigating Suspicious Microsoft 365 Mail Access by ClientAppId
- Verify the ClientAppId, source.ip and geolocation associated with Mail Access.
- Verify the total number of used ClientAppId by that specific user.id.
- Verify if the mailbox owner was on leave and just resumed working or not.
- Verify if there are other alerts associated with the same user.id.
- Verify the total number of connections from that ClientAppId, if it’s accessing other mailboxes and with a high frequency there is a high chance it’s a false positive.
False positive analysis
- Legit Microsoft or third party ClientAppId.
- User changing of ClientAppId or new connection post an extended period of leave.
- If the total number of accessed Mailboxes by ClientAppId is too high there is a high chance it’s a false positive.
Setup
editSetup
The Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.
Rule query
editevent.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:MailItemsAccessed and event.outcome:success and not o365.audit.ClientAppId : ("13937bba-652e-4c46-b222-3003f4d1ff97" or "6326e366-9d6d-4c70-b22a-34c7ea72d73d" or "a3883eba-fbe9-48bd-9ed3-dca3e0e84250" or "d3590ed6-52b3-4102-aeff-aad2292ab01c" or "27922004-5251-4030-b22d-91ecd9a37ea4" or "1fec8e78-bce4-4aaf-ab1b-5451cc387264" or "26a7ee05-5602-4d76-a7ba-eae8b7b67941" or "00000002-0000-0000-c000-000000000000" or "00000002-0000-0ff1-ce00-000000000000" or "ffcb16e8-f789-467c-8ce9-f826a080d987" or "00000003-0000-0ff1-ce00-000000000000" or "00000004-0000-0ff1-ce00-000000000000" or "00000005-0000-0ff1-ce00-000000000000" or "00000006-0000-0ff1-ce00-000000000000" or "00000007-0000-0000-c000-000000000000" or "00000007-0000-0ff1-ce00-000000000000" or "00000009-0000-0000-c000-000000000000" or "0000000c-0000-0000-c000-000000000000" or "00000015-0000-0000-c000-000000000000" or "0000001a-0000-0000-c000-000000000000" or "00b41c95-dab0-4487-9791-b9d2c32c80f2" or "022907d3-0f1b-48f7-badc-1ba6abab6d66" or "04b07795-8ddb-461a-bbee-02f9e1bf7b46" or "08e18876-6177-487e-b8b5-cf950c1e598c" or "0cb7b9ec-5336-483b-bc31-b15b5788de71" or "0cd196ee-71bf-4fd6-a57c-b491ffd4fb1e" or "0f698dd4-f011-4d23-a33e-b36416dcb1e6" or "13937bba-652e-4c46-b222-3003f4d1ff97" or "14d82eec-204b-4c2f-b7e8-296a70dab67e" or "16aeb910-ce68-41d1-9ac3-9e1673ac9575" or "1786c5ed-9644-47b2-8aa0-7201292175b6" or "17d5e35f-655b-4fb0-8ae6-86356e9a49f5" or "18fbca16-2224-45f6-85b0-f7bf2b39b3f3" or "1950a258-227b-4e31-a9cf-717495945fc2" or "1b3c667f-cde3-4090-b60b-3d2abd0117f0" or "1fec8e78-bce4-4aaf-ab1b-5451cc387264" or "20a11fe0-faa8-4df5-baf2-f965f8f9972e" or "23523755-3a2b-41ca-9315-f81f3f566a95" or "243c63a3-247d-41c5-9d83-7788c43f1c43" or "268761a2-03f3-40df-8a8b-c3db24145b6b" or "26a7ee05-5602-4d76-a7ba-eae8b7b67941" or "26abc9a8-24f0-4b11-8234-e86ede698878" or "27922004-5251-4030-b22d-91ecd9a37ea4" or "28b567f6-162c-4f54-99a0-6887f387bbcc" or "29d9ed98-a469-4536-ade2-f981bc1d605e" or "2abdc806-e091-4495-9b10-b04d93c3f040" or "2d4d3d8e-2be3-4bef-9f87-7875a61c29de" or "2d7f3606-b07d-41d1-b9d2-0d0c9296a6e8" or "3090ab82-f1c1-4cdf-af2c-5d7a6f3e2cc7" or "35d54a08-36c9-4847-9018-93934c62740c" or "37182072-3c9c-4f6a-a4b3-b3f91cacffce" or "38049638-cc2c-4cde-abe4-4479d721ed44" or "3c896ded-22c5-450f-91f6-3d1ef0848f6e" or "4345a7b9-9a63-4910-a426-35363201d503" or "45a330b1-b1ec-4cc1-9161-9f03992aa49f" or "4765445b-32c6-49b0-83e6-1d93765276ca" or "497effe9-df71-4043-a8bb-14cf78c4b63b" or "4b233688-031c-404b-9a80-a4f3f2351f90" or "4d5c2d63-cf83-4365-853c-925fd1a64357" or "51be292c-a17e-4f17-9a7e-4b661fb16dd2" or "5572c4c0-d078-44ce-b81c-6cbf8d3ed39e" or "5e3ce6c0-2b1f-4285-8d4b-75ee78787346" or "60c8bde5-3167-4f92-8fdb-059f6176dc0f" or "61109738-7d2b-4a0b-9fe3-660b1ff83505" or "62256cef-54c0-4cb4-bcac-4c67989bdc40" or "6253bca8-faf2-4587-8f2f-b056d80998a7" or "65d91a3d-ab74-42e6-8a2f-0add61688c74" or "66a88757-258c-4c72-893c-3e8bed4d6899" or "67e3df25-268a-4324-a550-0de1c7f97287" or "69893ee3-dd10-4b1c-832d-4870354be3d8" or "74658136-14ec-4630-ad9b-26e160ff0fc6" or "74bcdadc-2fdc-4bb3-8459-76d06952a0e9" or "797f4846-ba00-4fd7-ba43-dac1f8f63013" or "7ab7862c-4c57-491e-8a45-d52a7e023983" or "7ae974c5-1af7-4923-af3a-fb1fd14dcb7e" or "7b7531ad-5926-4f2d-8a1d-38495ad33e17" or "80ccca67-54bd-44ab-8625-4b79c4dc7775" or "835b2a73-6e10-4aa5-a979-21dfda45231c" or "871c010f-5e61-4fb1-83ac-98610a7e9110" or "89bee1f7-5e6e-4d8a-9f3d-ecd601259da7" or "8edd93e1-2103-40b4-bd70-6e34e586362d" or "905fcf26-4eb7-48a0-9ff0-8dcc7194b5ba" or "91ca2ca5-3b3e-41dd-ab65-809fa3dffffa" or "93625bc8-bfe2-437a-97e0-3d0060024faa" or "93d53678-613d-4013-afc1-62e9e444a0a5" or "944f0bd1-117b-4b1c-af26-804ed95e767e" or "94c63fef-13a3-47bc-8074-75af8c65887a" or "95de633a-083e-42f5-b444-a4295d8e9314" or "97cb1f73-50df-47d1-8fb0-0271f2728514" or "98db8bd6-0cc0-4e67-9de5-f187f1cd1b41" or "99b904fd-a1fe-455c-b86c-2f9fb1da7687" or "9ea1ad79-fdb6-4f9a-8bc3-2b70f96e34c7" or "a3475900-ccec-4a69-98f5-a65cd5dc5306" or "a3b79187-70b2-4139-83f9-6016c58cd27b" or "a57aca87-cbc0-4f3c-8b9e-dc095fdc8978" or "a970bac6-63fe-4ec5-8884-8536862c42d4" or "a9b49b65-0a12-430b-9540-c80b3332c127" or "ab9b8c07-8f02-4f72-87fa-80105867a763" or "ae8e128e-080f-4086-b0e3-4c19301ada69" or "b23dd4db-9142-4734-867f-3577f640ad0c" or "b4bddae8-ab25-483e-8670-df09b9f1d0ea" or "b669c6ea-1adf-453f-b8bc-6d526592b419" or "b6e69c34-5f1f-4c34-8cdf-7fea120b8670" or "bb2a2e3a-c5e7-4f0a-88e0-8e01fd3fc1f4" or "bdd48c81-3a58-4ea9-849c-ebea7f6b6360" or "c1c74fed-04c9-4704-80dc-9f79a2e515cb" or "c35cb2ba-f88b-4d15-aa9d-37bd443522e1" or "c44b4083-3bb0-49c1-b47d-974e53cbdf3c" or "c9a559d2-7aab-4f13-a6ed-e7e9c52aec87" or "cc15fd57-2c6c-4117-a88c-83b1d56b4bbe" or "cf36b471-5b44-428c-9ce7-313bf84528de" or "cf53fce8-def6-4aeb-8d30-b158e7b1cf83" or "d176f6e7-38e5-40c9-8a78-3998aab820e7" or "d3590ed6-52b3-4102-aeff-aad2292ab01c" or "d73f4b35-55c9-48c7-8b10-651f6f2acb2e" or "d9b8ec3a-1e4e-4e08-b3c2-5baf00c0fcb0" or "de8bc8b5-d9f9-48b1-a8ad-b748da725064" or "dfe74da8-9279-44ec-8fb2-2aed9e1c73d0" or "e1ef36fd-b883-4dbf-97f0-9ece4b576fc6" or "e64aa8bc-8eb4-40e2-898b-cf261a25954f" or "e9f49c6b-5ce5-44c8-925d-015017e9f7ad" or "ee272b19-4411-433f-8f28-5c13cb6fd407" or "f5eaa862-7f08-448c-9c4e-f4047d4d4521" or "fb78d390-0c51-40cd-8e17-fdbfab77341b" or "fc0f3af4-6835-4174-b806-f7db311fd2f3" or "fdf9885b-dd37-42bf-82e5-c3129ef5a302" )
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Initial Access
- ID: TA0001
- Reference URL: https://attack.mitre.org/tactics/TA0001/
-
Technique:
- Name: Valid Accounts
- ID: T1078
- Reference URL: https://attack.mitre.org/techniques/T1078/