DLP - PCI: US Credit Card Number (Any Network)

Severity: high
Type: rule
Source: github.com/sublime-security/sublime-rules

Detects outbound emails containing credit card numbers from any of the four major US payment networks — Visa, Mastercard (5-series and 2-series BINs), American Express, and Discover — in the message body or text-parseable attachments. This combined rule is suitable for broad PCI DLP coverage. For granular per-network alerting or tuning, use the individual network-specific rules instead: - dlp_pci_visa_credit_card.yml - dlp_pci_mastercard_credit_card.yml - dlp_pci_amex_credit_card.yml - dlp_pci_discover_credit_card.yml Card number formats matched (spaces and dashes as separators are supported): - Visa: 4XXX XXXX XXXX XXXX (16-digit) or 4XXX XXXX XXXXX (13-digit legacy) - Mastercard: 5[1-5]XX XXXX XXXX XXXX | 2[221-720]X XXXX XXXX XXXX - Amex: 3[47]XX XXXXXX XXXXX (15-digit, standard 4-6-5 grouping) - Discover: 6011 / 65XX / 64[4-9]X / 622126-622925 XXXX XXXX XXXX Regex engine: RE2 (Golang). No PCRE lookbehind — word boundaries (\b) are used instead. Attachment content is extracted via file.explode() / .scan.strings.strings. Deploy with the "Block Delivery" action to prevent PCI data exfiltration, or run passively for monitoring and audit logging.

Event coverage

Message attribute
attachments (collection)
body.current_thread
type

Rule body MQL

type.outbound
and (
  // ── Body scanning ─────────────────────────────────────────────────────────

  // Visa 16-digit
  regex.contains(body.current_thread.text, '\b4\d{3}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')

  // Visa 13-digit (legacy)
  or regex.contains(body.current_thread.text, '\b4\d{3}[\s-]?\d{4}[\s-]?\d{5}\b')

  // Mastercard 5-series (51–55)
  or regex.contains(body.current_thread.text, '\b5[1-5]\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')

  // Mastercard 2-series BINs (2221–2720)
  or regex.contains(body.current_thread.text,
    '\b(?:222[1-9]|22[3-9]\d|2[3-6]\d{2}|27[01]\d|2720)[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b'
  )

  // Amex 15-digit (34 or 37 prefix, 4-6-5 grouping)
  or regex.contains(body.current_thread.text, '\b3[47]\d{2}[\s-]?\d{6}[\s-]?\d{5}\b')

  // Discover 6011
  or regex.contains(body.current_thread.text, '\b6011[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')

  // Discover 65xx
  or regex.contains(body.current_thread.text, '\b65\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')

  // Discover 644–649
  or regex.contains(body.current_thread.text, '\b64[4-9]\d[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')

  // Discover/UnionPay co-branded 622126–622925
  or regex.contains(body.current_thread.text,
    '\b622(?:1(?:2[6-9]|[3-9]\d)|[2-8]\d{2}|9(?:[01]\d|2[0-5]))\d{2}[\s-]?\d{4}[\s-]?\d{4}\b'
  )

  // ── Attachment scanning ────────────────────────────────────────────────────

  or any(attachments,
    .file_extension in~ ('pdf', 'doc', 'docx', 'xls', 'xlsx', 'txt', 'csv', 'eml', 'msg')
    and any(file.explode(.),
      any(.scan.strings.strings,
        // Visa 16-digit
        regex.contains(., '\b4\d{3}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')
        // Visa 13-digit
        or regex.contains(., '\b4\d{3}[\s-]?\d{4}[\s-]?\d{5}\b')
        // Mastercard 5-series
        or regex.contains(., '\b5[1-5]\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')
        // Mastercard 2-series
        or regex.contains(.,
          '\b(?:222[1-9]|22[3-9]\d|2[3-6]\d{2}|27[01]\d|2720)[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b'
        )
        // Amex
        or regex.contains(., '\b3[47]\d{2}[\s-]?\d{6}[\s-]?\d{5}\b')
        // Discover 6011
        or regex.contains(., '\b6011[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')
        // Discover 65xx
        or regex.contains(., '\b65\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')
        // Discover 644-649
        or regex.contains(., '\b64[4-9]\d[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b')
        // Discover/UnionPay 622126-622925
        or regex.contains(.,
          '\b622(?:1(?:2[6-9]|[3-9]\d)|[2-8]\d{2}|9(?:[01]\d|2[0-5]))\d{2}[\s-]?\d{4}[\s-]?\d{4}\b'
        )
      )
    )
  )
)

Detection logic

Scope: outbound message.

outbound message
any of:
- body.current_thread.text matches '\\b4\\d{3}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b4\\d{3}[\\s-]?\\d{4}[\\s-]?\\d{5}\\b'
- body.current_thread.text matches '\\b5[1-5]\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b(?:222[1-9]|22[3-9]\\d|2[3-6]\\d{2}|27[01]\\d|2720)[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b3[47]\\d{2}[\\s-]?\\d{6}[\\s-]?\\d{5}\\b'
- body.current_thread.text matches '\\b6011[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b65\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b64[4-9]\\d[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- body.current_thread.text matches '\\b622(?:1(?:2[6-9]|[3-9]\\d)|[2-8]\\d{2}|9(?:[01]\\d|2[0-5]))\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
- any of attachments where all hold:
  - .file_extension in ('pdf', 'doc', 'docx', 'xls', 'xlsx', 'txt', 'csv', 'eml', 'msg')
  - any of file.explode(.) where:
    
    any of .scan.strings.strings where any holds:
    
    . matches '\\b4\\d{3}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b4\\d{3}[\\s-]?\\d{4}[\\s-]?\\d{5}\\b'
    . matches '\\b5[1-5]\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b(?:222[1-9]|22[3-9]\\d|2[3-6]\\d{2}|27[01]\\d|2720)[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b3[47]\\d{2}[\\s-]?\\d{6}[\\s-]?\\d{5}\\b'
    . matches '\\b6011[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b65\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b64[4-9]\\d[\\s-]?\\d{4}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'
    . matches '\\b622(?:1(?:2[6-9]|[3-9]\\d)|[2-8]\\d{2}|9(?:[01]\\d|2[0-5]))\\d{2}[\\s-]?\\d{4}[\\s-]?\\d{4}\\b'

Inspects: attachments[].file_extension, body.current_thread.text, type.outbound. Sensors: file.explode, regex.contains.

Indicators matched (18)

Field	Match	Value
`regex.contains`	regex	`\b4\d{3}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b4\d{3}[\s-]?\d{4}[\s-]?\d{5}\b`
`regex.contains`	regex	`\b5[1-5]\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b(?:222[1-9]\|22[3-9]\d\|2[3-6]\d{2}\|27[01]\d\|2720)[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b3[47]\d{2}[\s-]?\d{6}[\s-]?\d{5}\b`
`regex.contains`	regex	`\b6011[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b65\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b64[4-9]\d[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b`
`regex.contains`	regex	`\b622(?:1(?:2[6-9]\|[3-9]\d)\|[2-8]\d{2}\|9(?:[01]\d\|2[0-5]))\d{2}[\s-]?\d{4}[\s-]?\d{4}\b`
`attachments[].file_extension`	member	`pdf`
`attachments[].file_extension`	member	`doc`
`attachments[].file_extension`	member	`docx`

6 more

`attachments[].file_extension`	member	`xls`
`attachments[].file_extension`	member	`xlsx`
`attachments[].file_extension`	member	`txt`
`attachments[].file_extension`	member	`csv`
`attachments[].file_extension`	member	`eml`
`attachments[].file_extension`	member	`msg`

`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)

DLP - PCI: US Credit Card Number (Any Network)

Event coverage

Rule body MQL

Detection logic

Indicators matched (18)

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