Cleartext Protocol Usage

Status: stable
Severity: low
Log source: category firewall
Author: Alexandr Yampolskyi, SOC Prime, Tim Shelton
Source: github.com/SigmaHQ/sigma

Ensure that all account usernames and authentication credentials are transmitted across networks using encrypted channels. Ensure that an encryption is used for all sensitive information in transit. Ensure that an encrypted channels is used for all administrative account access.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	No specific technique

Rule body yaml

title: Cleartext Protocol Usage
id: d7fb8f0e-bd5f-45c2-b467-19571c490d7e
status: stable
description: |
    Ensure that all account usernames and authentication credentials are transmitted across networks using encrypted channels.
    Ensure that an encryption is used for all sensitive information in transit. Ensure that an encrypted channels is used for all administrative account access.
references:
    - https://www.cisecurity.org/controls/cis-controls-list/
    - https://www.pcisecuritystandards.org/documents/PCI_DSS_v3-2-1.pdf
    - https://nvlpubs.nist.gov/nistpubs/CSWP/NIST.CSWP.04162018.pdf
author: Alexandr Yampolskyi, SOC Prime, Tim Shelton
date: 2019-03-26
modified: 2022-10-10
tags:
    - attack.credential-access
    # - CSC4
    # - CSC4.5
    # - CSC14
    # - CSC14.4
    # - CSC16
    # - CSC16.5
    # - NIST CSF 1.1 PR.AT-2
    # - NIST CSF 1.1 PR.MA-2
    # - NIST CSF 1.1 PR.PT-3
    # - NIST CSF 1.1 PR.AC-1
    # - NIST CSF 1.1 PR.AC-4
    # - NIST CSF 1.1 PR.AC-5
    # - NIST CSF 1.1 PR.AC-6
    # - NIST CSF 1.1 PR.AC-7
    # - NIST CSF 1.1 PR.DS-1
    # - NIST CSF 1.1 PR.DS-2
    # - ISO 27002-2013 A.9.2.1
    # - ISO 27002-2013 A.9.2.2
    # - ISO 27002-2013 A.9.2.3
    # - ISO 27002-2013 A.9.2.4
    # - ISO 27002-2013 A.9.2.5
    # - ISO 27002-2013 A.9.2.6
    # - ISO 27002-2013 A.9.3.1
    # - ISO 27002-2013 A.9.4.1
    # - ISO 27002-2013 A.9.4.2
    # - ISO 27002-2013 A.9.4.3
    # - ISO 27002-2013 A.9.4.4
    # - ISO 27002-2013 A.8.3.1
    # - ISO 27002-2013 A.9.1.1
    # - ISO 27002-2013 A.10.1.1
    # - PCI DSS 3.2 2.1
    # - PCI DSS 3.2 8.1
    # - PCI DSS 3.2 8.2
    # - PCI DSS 3.2 8.3
    # - PCI DSS 3.2 8.7
    # - PCI DSS 3.2 8.8
    # - PCI DSS 3.2 1.3
    # - PCI DSS 3.2 1.4
    # - PCI DSS 3.2 4.3
    # - PCI DSS 3.2 7.1
    # - PCI DSS 3.2 7.2
    # - PCI DSS 3.2 7.3
logsource:
    category: firewall
detection:
    selection:
        dst_port:
            - 8080
            - 21
            - 80
            - 23
            - 50000
            - 1521
            - 27017
            - 3306
            - 1433
            - 11211
            - 15672
            - 5900
            - 5901
            - 5902
            - 5903
            - 5904
    selection_allow1:
        action:
            - forward
            - accept
            - 2
    selection_allow2:
        blocked: "false" # not all fws set action value, but are set to mark as blocked or allowed or not
    condition: selection and 1 of selection_allow*
falsepositives:
    - Unknown
level: low

Stages and Predicates

Stage 0: `condition`

selection and 1 of selection_allow*

Stage 1: `selection`

Stage 2: `selection_allow1`

selection_allow1:
    action:
        - forward
        - accept
        - 2

Stage 3: `selection_allow2`

selection_allow2:
    blocked: "false"

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
`action`	eq	`2` `accept` `forward`
`blocked`	eq	`false`
`dst_port`	eq	`11211` `1433` `1521` `15672` `21` `23` `27017` `3306` `50000` `5900` `5901` `5902` `5903` `5904` `80` `8080`

`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)

Cleartext Protocol Usage

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `selection_allow1`

Stage 3: `selection_allow2`

Indicators

Keyboard shortcuts

Search operators

Cleartext Protocol Usage

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: selection_allow1

Stage 3: selection_allow2

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `selection_allow1`

Stage 3: `selection_allow2`