Potential Bucket Enumeration on AWS

Status: test
Severity: low
Log source: product aws, service cloudtrail
Author: Christopher Peacock @securepeacock, SCYTHE @scythe_io
Source: github.com/SigmaHQ/sigma

Looks for potential enumeration of AWS buckets via ListBuckets.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1580` Cloud Infrastructure Discovery, `T1619` Cloud Storage Object Discovery

Event coverage

Provider	Event
AWS-s3	ListBuckets

Rules detecting the same action

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

AWS Discovery API Calls from VPN ASN for the First Time by Identity (Elastic)

Rule body yaml

title: Potential Bucket Enumeration on AWS
id: f305fd62-beca-47da-ad95-7690a0620084
related:
    - id: 4723218f-2048-41f6-bcb0-417f2d784f61
      type: similar
status: test
description: Looks for potential enumeration of AWS buckets via ListBuckets.
references:
    - https://github.com/Lifka/hacking-resources/blob/c2ae355d381bd0c9f0b32c4ead049f44e5b1573f/cloud-hacking-cheat-sheets.md
    - https://jamesonhacking.blogspot.com/2020/12/pivoting-to-private-aws-s3-buckets.html
    - https://securitycafe.ro/2022/12/14/aws-enumeration-part-ii-practical-enumeration/
author: Christopher Peacock @securepeacock, SCYTHE @scythe_io
date: 2023-01-06
modified: 2024-07-10
tags:
    - attack.discovery
    - attack.t1580
    - attack.t1619
logsource:
    product: aws
    service: cloudtrail
detection:
    selection:
        eventSource: 's3.amazonaws.com'
        eventName: 'ListBuckets'
    filter:
        userIdentity.type: 'AssumedRole'
    condition: selection and not filter
falsepositives:
    - Administrators listing buckets, it may be necessary to filter out users who commonly conduct this activity.
level: low

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    eventSource: 's3.amazonaws.com'
    eventName: 'ListBuckets'

Stage 2: `not filter`

filter:
    userIdentity.type: 'AssumedRole'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`userIdentity.type`	eq	`AssumedRole`

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
`eventName`	eq	`ListBuckets`
`eventSource`	eq	`s3.amazonaws.com`

`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)

Potential Bucket Enumeration on AWS

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Potential Bucket Enumeration on AWS

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter`