macOS Cloud Storage Access Tools

Status: experimental
Severity: medium
Log source: product macos, service endpointsecurity
Author: Eric Brown - Nebulock, Inc.
Source: github.com/Nebulock-Inc/macos-coresigma

Detects execution of cloud storage CLI tools (aws, gsutil, rclone) which may indicate exfiltration to cloud storage services. Adversaries use cloud storage to exfiltrate data while blending in with legitimate traffic.

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1537` Transfer Data to Cloud Account, `T1567.002` Exfiltration Over Web Service: Exfiltration to Cloud Storage

Rule body yaml

title: macOS Cloud Storage Access Tools
id: 4a0366e3-01e0-4345-bf41-487b54871df7
status: experimental
description: 'Detects execution of cloud storage CLI tools (aws, gsutil, rclone) which
  may

  indicate exfiltration to cloud storage services. Adversaries use cloud storage

  to exfiltrate data while blending in with legitimate traffic.

  '
author: Eric Brown - Nebulock, Inc.
date: 2025/10/31
modified: 2025/10/31
references:
- https://attack.mitre.org/techniques/T1567/002/
- https://attack.mitre.org/techniques/T1537/
logsource:
  product: macos
  service: endpointsecurity
detection:
  selection_event:
    esf.event_type: 9
    event.action: exec
  selection_process:
    Image|endswith:
    - /aws
    - /gsutil
    - /rclone
    - /s3cmd
    - /azcopy
  selection_upload:
    CommandLine|contains:
    - s3 cp
    - s3 sync
    - gsutil cp
    - rclone copy
    - rclone sync
    - put
    - upload
  condition: selection_event and selection_process and selection_upload
falsepositives:
- Legitimate cloud backup operations
- DevOps and CI/CD pipelines
- Automated data synchronization
- System administration tasks
fields:
- Image
- CommandLine
- ProcessId
- ParentProcessId
- User
tags:
- attack.exfiltration
- attack.t1567.002
- attack.t1537
level: medium

Stages and Predicates

Stage 0: `condition`

selection_event and selection_process and selection_upload

Stage 1: `selection_event`

selection_event:
  esf.event_type: 9
  event.action: exec

Stage 2: `selection_process`

selection_process:
  Image|endswith:
  - /aws
  - /gsutil
  - /rclone
  - /s3cmd
  - /azcopy

Stage 3: `selection_upload`

selection_upload:
  CommandLine|contains:
  - s3 cp
  - s3 sync
  - gsutil cp
  - rclone copy
  - rclone sync
  - put
  - upload

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
`CommandLine`	match	`gsutil cp` `put` `rclone copy` `rclone sync` `s3 cp` `s3 sync` `upload`
`Image`	ends_with	`/aws` `/azcopy` `/gsutil` `/rclone` `/s3cmd`
`esf.event_type`	eq	`9`
`event.action`	eq	`exec`

`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)

macOS Cloud Storage Access Tools

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_event`

Stage 2: `selection_process`

Stage 3: `selection_upload`

Indicators

Keyboard shortcuts

Search operators

macOS Cloud Storage Access Tools

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_event

Stage 2: selection_process

Stage 3: selection_upload

Indicators

Stage 0: `condition`

Stage 1: `selection_event`

Stage 2: `selection_process`

Stage 3: `selection_upload`