AWSCloudTrail - Successful brute force attack on S3 Bucket

Status: available
Severity: high
Time window: 1h
Group by: AccountName, AccountUPNSuffix, RecipientAccountId, SourceIpAddress, UserIdentityAccountId, bucketName
Source: github.com/Azure/Azure-Sentinel

Detects repeated failed GetObject attempts against an S3 bucket followed by a successful access from the same source, which can indicate brute-force-style object discovery or access attempts.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110` Brute Force

Rules detecting the same action

Other rules on this platform that filter on the same API call or operation.

Rule body kusto

id: 31b9e94b-0df6-4a3d-a297-3457b53c5d86
name: AWSCloudTrail - Successful brute force attack on S3 Bucket
description: |
  Detects repeated failed GetObject attempts against an S3 bucket followed by a successful access from the
  same source, which can indicate brute-force-style object discovery or access attempts.
severity: High
status: Available
requiredDataConnectors:
  - connectorId: AWS
    dataTypes:
      - AWSCloudTrail
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |
    let timeframe = 1h;
    let failed_attempts = AWSCloudTrail
    | where TimeGenerated >= ago(timeframe)
    | where EventName == "GetObject" and isnotempty(ErrorMessage) and isnotempty(ErrorCode)
    | where UserIdentityAccountId == "ANONYMOUS_PRINCIPAL" or UserIdentityAccessKeyId <> RecipientAccountId
    | extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
    | extend UserName = tostring(split(UserIdentityArn, '/')[-1])
    | extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
    | extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
      AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
    | extend bucketName = tostring(parse_json(RequestParameters).bucketName), keyName = tostring(parse_json(RequestParameters).key)
    | summarize time_min_failed=arg_min(TimeGenerated, *), failed_keys = dcount(keyName) by RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, SourceIpAddress, bucketName
    | where failed_keys > 20;
    let success_attempts = AWSCloudTrail
    | where TimeGenerated >= ago(timeframe)
    | where EventName == "GetObject" and isempty(ErrorMessage) and isempty(ErrorCode)
    | where UserIdentityAccountId == "ANONYMOUS_PRINCIPAL" or UserIdentityAccessKeyId <> RecipientAccountId
    | extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
    | extend UserName = tostring(split(UserIdentityArn, '/')[-1])
    | extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
    | extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
      AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
    | extend bucketName = tostring(parse_json(RequestParameters).bucketName), keyName = tostring(parse_json(RequestParameters).key)
    | summarize time_min_success=arg_min(TimeGenerated, *), success_keys = dcount(keyName) by RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, SourceIpAddress, bucketName
    | where success_keys >= 1;
    failed_attempts
    | join kind=inner success_attempts on SourceIpAddress, RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, bucketName
    | where time_min_success > time_min_failed
    | project-away keyName
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
      - identifier: CloudAppAccountId
        columnName: RecipientAccountId
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIpAddress
customDetails:
  bucketName: bucketName
  failed_keys: failed_keys
  success_keys: success_keys
  RecipientAccountId: RecipientAccountId
alertDetailsOverride:
  alertDisplayNameFormat: 'AWS S3 brute force pattern detected from {{SourceIpAddress}}'
  alertDescriptionFormat: 'Detected repeated failed and then successful S3 GetObject access for bucket {{bucketName}} in account {{RecipientAccountId}}.'
version: 1.0.2
kind: Scheduled

Stages and Predicates

Parameters

let timeframe = 1h;

Let binding: `success_attempts`

let success_attempts = AWSCloudTrail
| where TimeGenerated >= ago(timeframe)
| where EventName == "GetObject" and isempty(ErrorMessage) and isempty(ErrorCode)
| where UserIdentityAccountId == "ANONYMOUS_PRINCIPAL" or UserIdentityAccessKeyId <> RecipientAccountId
| extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
| extend UserName = tostring(split(UserIdentityArn, '/')[-1])
| extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
| extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
  AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
| extend bucketName = tostring(parse_json(RequestParameters).bucketName), keyName = tostring(parse_json(RequestParameters).key)
| summarize time_min_success=arg_min(TimeGenerated, *), success_keys = dcount(keyName) by RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, SourceIpAddress, bucketName
| where success_keys >= 1;

Derived from timeframe.

The stages below define let failed_attempts (the rule's main pipeline source).

Stage 1: `source`

AWSCloudTrail

Stage 2: `where`

| where TimeGenerated >= ago(timeframe)

Stage 3: `where`

| where EventName == "GetObject" and isnotempty(ErrorMessage) and isnotempty(ErrorCode)

Stage 4: `where`

| where UserIdentityAccountId == "ANONYMOUS_PRINCIPAL" or UserIdentityAccessKeyId <> RecipientAccountId

Stage 5: `extend` (5 consecutive steps)

| extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
| extend UserName = tostring(split(UserIdentityArn, '/')[-1])
| extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
| extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
  AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
| extend bucketName = tostring(parse_json(RequestParameters).bucketName), keyName = tostring(parse_json(RequestParameters).key)

Stage 6: `summarize`

| summarize time_min_failed=arg_min(TimeGenerated, *), failed_keys = dcount(keyName) by RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, SourceIpAddress, bucketName

Threshold: gt 20

Stage 7: `where`

| where failed_keys > 20

The stages below run on failed_attempts (the outer pipeline).

Stage 8: `join`

failed_attempts
| join kind=inner success_attempts on SourceIpAddress, RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityAccountId, bucketName

Stage 9: `where`

| where time_min_success > time_min_failed

Stage 10: `project-away`

| project-away keyName

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`ErrorCode`	is_not_null	(no value, null check)
`ErrorCode`	is_null	(no value, null check)
`ErrorMessage`	is_not_null	(no value, null check)
`ErrorMessage`	is_null	(no value, null check)
`EventName`	eq	`GetObject` transforms: `cased`
`UserIdentityAccessKeyId`	ne	`RecipientAccountId` transforms: `cased`
`UserIdentityAccountId`	eq	`ANONYMOUS_PRINCIPAL` transforms: `cased`
`failed_keys`	gt	`20` transforms: `cased`
`success_keys`	ge	`1` transforms: `cased`
`time_min_success`	gt	`time_min_failed` transforms: `cased`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`AccountName`	`summarize`
`AccountUPNSuffix`	`summarize`
`RecipientAccountId`	`summarize`
`SourceIpAddress`	`summarize`
`UserIdentityAccountId`	`summarize`
`bucketName`	`summarize`
`failed_keys`	`summarize`
`time_min_failed`	`summarize`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

AWSCloudTrail - Successful brute force attack on S3 Bucket

MITRE ATT&CK coverage

Rules detecting the same action

Rule body kusto

Stages and Predicates

Parameters

Let binding: `success_attempts`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend` (5 consecutive steps)

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `join`

Stage 9: `where`

Stage 10: `project-away`

Indicators

Output fields

Keyboard shortcuts

Search operators

AWSCloudTrail - Successful brute force attack on S3 Bucket

MITRE ATT&CK coverage

Rules detecting the same action

Rule body kusto

Stages and Predicates

Parameters

Let binding: success_attempts

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: extend (5 consecutive steps)

Stage 6: summarize

Stage 7: where

Stage 8: join

Stage 9: where

Stage 10: project-away

Indicators

Output fields

Let binding: `success_attempts`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend` (5 consecutive steps)

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `join`

Stage 9: `where`

Stage 10: `project-away`