macOS Remote Execution Tools

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

Detects execution of remote execution and terminal multiplexer tools (screen, tmux) often used by adversaries for maintaining persistent sessions or executing commands on remote systems during lateral movement.

MITRE ATT&CK coverage

Tactic	Techniques
Lateral Movement	`T1021` Remote Services, `T1563` Remote Service Session Hijacking

Rule body yaml

title: macOS Remote Execution Tools
id: a52677c9-2670-428b-919a-95df34338e2c
status: experimental
description: 'Detects execution of remote execution and terminal multiplexer tools
  (screen, tmux)

  often used by adversaries for maintaining persistent sessions or executing commands

  on remote systems during lateral movement.

  '
author: Eric Brown - Nebulock, Inc.
date: 2025/10/31
modified: 2025/10/31
references:
- https://attack.mitre.org/techniques/T1021/
- https://attack.mitre.org/techniques/T1563/
logsource:
  product: macos
  service: endpointsecurity
detection:
  selection_event:
    esf.event_type: 9
    event.action: exec
  selection_process:
    Image|endswith:
    - /screen
    - /tmux
    - /expect
  condition: selection_event and selection_process
falsepositives:
- Legitimate use of terminal multiplexers by developers and administrators
- Automated scripts using expect for interactive command execution
- Remote administration sessions
fields:
- Image
- CommandLine
- ProcessId
- ParentProcessId
- User
tags:
- attack.lateral_movement
- attack.t1021
- attack.t1563
level: low

Stages and Predicates

Stage 0: `condition`

selection_event and selection_process

Stage 1: `selection_event`

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

Stage 2: `selection_process`

selection_process:
  Image|endswith:
  - /screen
  - /tmux
  - /expect

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
`Image`	ends_with	`/expect` `/screen` `/tmux`
`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 Remote Execution Tools

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_event`

Stage 2: `selection_process`

Indicators

Keyboard shortcuts

Search operators

macOS Remote Execution Tools

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_event

Stage 2: selection_process

Indicators

Stage 0: `condition`

Stage 1: `selection_event`

Stage 2: `selection_process`