Elastic Security Detection Rules

Suspicious Microsoft 365 Mail Access by Unusual ClientAppId

Last updated 2 months ago on 2025-06-16
Created 2 years ago on 2023-07-18

About

Identifies suspicious Microsoft 365 mail access by ClientAppId. This rule detects when a user accesses their mailbox using a client application that is not typically used by the user, which may indicate potential compromise or unauthorized access attempts. Adversaries may use custom or third-party applications to access mailboxes, bypassing standard security controls. First-party Microsoft applications are also abused after OAuth tokens are compromised, allowing adversaries to access mailboxes without raising suspicion.
Tags
Domain: CloudDomain: EmailData Source: Microsoft 365Data Source: Microsoft 365 Audit LogsUse Case: Threat DetectionTactic: CollectionLanguage: kuery
Severity
medium
Risk Score
47
MITRE ATT&CK™

Collection (TA0009)(opens in a new tab or window)

↳ Email Collection (T1114)(opens in a new tab or window)

False Positive Examples
User using a new mail client or mobile application to access their mailbox. Users accessing their mailboxes using custom or third-party applications that are authorized by the organization, such as CRM or ERP systems. Users accessing their mailboxes using first-party Microsoft applications that are not typically used by the user, such as Outlook on the web or Outlook mobile app.
License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
New Terms Rule
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
filebeat-*logs-o365.audit-*
Related Integrations

o365(opens in a new tab or window)

Query
event.dataset: "o365.audit" and
    event.provider: "Exchange" and
    event.category: "web" and
    event.action: "MailItemsAccessed" and
    event.outcome: "success" and
    o365.audit.LogonType: ("0" or "1" or "6") and
    o365.audit.UserType: ("0" or "2" or "3" or "10") and
    o365.audit.OperationProperties.Value: "Bind" and
    not o365.audit.ClientAppId : (
        "00000002-0000-0000-c000-000000000000" or "00000002-0000-0ff1-ce00-000000000000" 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
        "00000012-0000-0000-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
        "08543e9e-5b1f-4af5-8228-cb5a5c9d4e24" 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 "1150aefc-07de-4228-b2b2-042a536703c0" or
        "11ba4a52-3159-44e1-93cd-d18e9443e3ef" or "13937bba-652e-4c46-b222-3003f4d1ff97" or
        "13937bba-652e-4c46-b222-3003f4d1ff97" or "13937bba-652e-4c46-b222-3003f4d1ff97" or
        "14d82eec-204b-4c2f-b7e8-296a70dab67e" or "157cdfbf-7398-4a56-96c3-e93e9ab309b5" 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 "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 "26a7ee05-5602-4d76-a7ba-eae8b7b67941" or
        "26abc9a8-24f0-4b11-8234-e86ede698878" or "27922004-5251-4030-b22d-91ecd9a37ea4" or
        "27922004-5251-4030-b22d-91ecd9a37ea4" or "27b9c0f2-3d8e-4a1c-8b6f-5d7a0c6e1f2b" or
        "28b567f6-162c-4f54-99a0-6887f387bbcc" or "29d9ed98-a469-4536-ade2-f981bc1d605e" or
        "2abdc806-e091-4495-9b10-b04d93c3f040" or "2cee05de-2b8f-45a2-8289-2a06ca32c4c8" or
        "2d4d3d8e-2be3-4bef-9f87-7875a61c29de" or "2d7f3606-b07d-41d1-b9d2-0d0c9296a6e8" or
        "2fd64745-b008-3e7d-4903-15d43e60f62a" 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
        "43375d74-c6a5-4d4e-a0a3-de139860ea75" or "4345a7b9-9a63-4910-a426-35363201d503" or
        "45a330b1-b1ec-4cc1-9161-9f03992aa49f" or "464e0e4d-676a-4c3b-9f81-2ed9b2a9acd2" 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
        "5d661950-3475-41cd-a2c3-d671a3162bc1" 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
        "6326e366-9d6d-4c70-b22a-34c7ea72d73d" 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 "75efb5bc-18a1-4e7b-8a66-2ad2503d79c6" or
        "75f31797-37c9-498e-8dc9-53c16a36afca" 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 "7fba38f4-ec1f-458d-906c-f4e3c4f41335" or
        "80ccca67-54bd-44ab-8625-4b79c4dc7775" or "82d8ab62-be52-a567-14ea-1616c4ee06c4" or
        "835b2a73-6e10-4aa5-a979-21dfda45231c" or "871c010f-5e61-4fb1-83ac-98610a7e9110" or
        "89bee1f7-5e6e-4d8a-9f3d-ecd601259da7" or "8acd33ea-7197-4a96-bc33-d7cc7101262f" or
        "8edd93e1-2103-40b4-bd70-6e34e586362d" or "905fcf26-4eb7-48a0-9ff0-8dcc7194b5ba" or
        "9199bf20-a13f-4107-85dc-02114787ef48" or "9199bf20-a13f-4107-85dc-02114787ef48" 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
        "9fd38622-d9b4-4401-b1b9-1ce14c5e435a" or "a3475900-ccec-4a69-98f5-a65cd5dc5306" or
        "a3883eba-fbe9-48bd-9ed3-dca3e0e84250" or "a3883eba-fbe9-48bd-9ed3-dca3e0e84250" or
        "a3b79187-70b2-4139-83f9-6016c58cd27b" or "a40d7d7d-59aa-447e-a655-679a4107e548" 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 "d34dcd43-8519-44e4-827c-de79b767da47" or
        "d3590ed6-52b3-4102-aeff-aad2292ab01c" or "d3590ed6-52b3-4102-aeff-aad2292ab01c" or
        "d3590ed6-52b3-4102-aeff-aad2292ab01c" or "d396de1f-10d4-4023-aae2-5bb3d724ba9a" or
        "d71dfe16-1070-48f3-bd3a-c3ec919d34e7" 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 "e9b154d0-7658-433b-bb25-6b8e0a8a7c59" or
        "e9f49c6b-5ce5-44c8-925d-015017e9f7ad" or "ee272b19-4411-433f-8f28-5c13cb6fd407" or
        "eed83176-464d-48c7-a887-cc5cc534c7b8" or "f5eaa862-7f08-448c-9c4e-f4047d4d4521" or
        "f8d98a96-0999-43f5-8af3-69971c7bb423" or "fb78d390-0c51-40cd-8e17-fdbfab77341b" or
        "fc0f3af4-6835-4174-b806-f7db311fd2f3" or "fdf9885b-dd37-42bf-82e5-c3129ef5a302" or
        "ffcb16e8-f789-467c-8ce9-f826a080d987"
    )

Install detection rules in Elastic Security

Detect Suspicious Microsoft 365 Mail Access by Unusual ClientAppId in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).