Sublime Security low experimental mql

Extortion / sextortion (untrusted sender)

Detects extortion and sextortion attempts by analyzing the email body text from an untrusted sender.

View Source

Detection Logic

type.inbound
and length(filter(body.links, .display_text is not null)) < 10
and not (
  ml.nlu_classifier(body.current_thread.text).language == "english"
  and any(ml.nlu_classifier(body.html.display_text).topics,
          .name in (
            "News and Current Events",
            "Newsletters and Digests",
            "Advertising and Promotions"
          )
          and .confidence in ("high", "medium")
  )
)
and (
  (
    any(ml.nlu_classifier(strings.replace_confusables(body.current_thread.text)).intents,
        (.name == "extortion" and .confidence == "high")
    )
    and (
      any(ml.nlu_classifier(strings.replace_confusables(body.current_thread.text
                            )
          ).entities,
          .name == "financial"
          or (
            .name is not null
            and regex.icontains(.text,
                                "cybḛ[rŗřṙȑȓɍʀɼɽг]c[rŗřṙȑȓɍʀɼɽг]imina[lĺļľḷḹḽłƖʟḻ]s"
            )
          )
      )
      or any(ml.nlu_classifier(strings.replace_confusables(body.current_thread.text
                               )
             ).topics,
             .name == "Financial Communications" and .confidence != "low"
      )
    )
  )
  // catches extortion content delivered as inline base64 images
  or (
    (body.current_thread.text is null or length(body.current_thread.text) < 100)
    and any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).intents,
            .name == "extortion" and .confidence == "high"
    )
    and (
      any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).entities,
          .name == "financial"
      )
      or any(ml.nlu_classifier(beta.ocr(file.message_screenshot()).text).topics,
             .name == "Financial Communications" and .confidence != "low"
      )
    )
  )
  // manual indicators failsafe
  or 3 of (
    // malware terms
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    "(?:(?:spy
| [mṁ][aȁḁ]l)[wŵ][aȁḁ][rŗ]e
| [tŢ][rŗȓ][oốởộ]j[aǻä][nņ]
| [rȓ]emote (?:entry
| cont[rř]o[lĺ])
| infiltrat(?:ed
| ion)
| backdoor
| vi[rṙ]us
| intruder
| (?:your
| the).{0,15}(?:device
| system
| computer
| phone).{0,10}(?:became
| was
| got
| is).{0,5}comprom[ḯiïíįī]sed
| prov[ḯiïíįī]d[ḯiïíįī]ng.{0,20}full [aảǡą]ccess)"
    ),
    // actions recorded
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    "(?:p[oộ][rŗ]n
| a[dȡ]ult (?:web)?site
| webcam
| mastu[rŗ]bating
| je[rŗ]king off
| pleasu[rŗȑ]i[nŋ]g you[rŗṛ]self
| getting off
| expli[cƈ]it
| cl[ḯiïíįī]ps.{0,20}screenshots
| NSFW
| gr[aǻẳ]phic c[oỡở]ntent)"
    ),
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    "(?:pe[rŗ]ve[rŗ]t
| pe[rŗ]ve[rŗ]sion
| mastu[rŗ]bat)"
    ),
    // a timeframe to pay
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    '[ilo0-9]{2} (?:hou[rŗṝ][sṣ]
| uu[rŗ])',
                    '(?:one
| tw[oờȍ]
| 2
| th[rŗ]ee
| \d) [dḍ][aảǡą]y[sṣ]?',
                    'set a timer'
    ),
    // a promise from the actor
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    '(?:pe[rŗ]manently
| will
| I''ll) delete
| ([rŗ]emove
| destroy) (?:[\p{L}\p{M}\p{N}]+\s*){0,4} (?:data
| ev[ḯiïįīí]dence
| v[ḯiïíįī]deos?)'
    ),
    // a threat from the actor
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    '(?:\bsen[dt]
| forward
| expose
| share)\s*(?:[\p{L}\p{N}]+\s*){0,5}\s*to\s*(?:[\p{L}\p{N}]+\s*){0,5}(?:contacts
| media
| family
| f[rŗ]iends
| coworkers
| co-workers
| associates
| kin\b)'
    ),
    // bitcoin language (excluding newsletters)
    (
      regex.icontains(strings.replace_confusables(body.current_thread.text),
                      '[bḆḂ]i[tṯ][cĉƈ][oöة]i[nņɲň]
| \bbtc\b
| blockchain'
      )
      // negate cryptocurrency newsletters
      and not (
        any(body.links,
            strings.icontains(.display_text, "unsubscribe")
            and (
              strings.icontains(.href_url.path, "unsubscribe")
              // handle mimecast URL rewrites
              or (
                .href_url.domain.root_domain == 'mimecastprotect.com'
                and strings.icontains(.href_url.query_params,
                                      sender.email.domain.root_domain
                )
              )
            )
        )
      )
    ),
    (
      regex.icontains(strings.replace_confusables(body.current_thread.text),
                      '(?:contact the police
| (?:bitcoin
| \bbtc\b).{0,20}(?:wallet
| address))'
      )
      and regex.icontains(strings.replace_confusables(body.current_thread.text),
                          '(?:\b[13][a-km-zA-HJ-NP-Z0-9]{24,34}\b)
| \bX[1-9A-HJ-NP-Za-km-z]{33}\b
| \b(?:0x[a-fA-F0-9]{40})\b
| \b[LM3][a-km-zA-HJ-NP-Z1-9]{26,33}\b
| \b[48][0-9AB][1-9A-HJ-NP-Za-km-z]{93}\b'
      )
    ),
    regex.icontains(strings.replace_confusables(body.current_thread.text),
                    'bc1q.{0,50}\b'
    ),
    (
      regex.count(body.current_thread.text,
                  '[\x{0300}-\x{036F}\x{1AB0}-\x{1AFF}\x{1DC0}-\x{1DFF}\x{0100}-\x{024F}\x{1E00}-\x{1EFF}]'
      ) > 20
      and length(body.current_thread.links) == 0
    )
  )
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
  or any(headers.hops, any(.fields, .name == "X-Google-Group-Id"))

  // many extortion emails spoof sender domains and fail sender authentication
  or (
    not headers.auth_summary.dmarc.pass
    or headers.auth_summary.dmarc.pass is null
    or not headers.auth_summary.spf.pass
  )
)
// negate legit bounce backs
and not any(ml.nlu_classifier(body.current_thread.text).topics,
            .name in ("Bounce Back and Delivery Failure Notifications")
)
// negate legit forwards and replies
and not (
  (subject.is_reply or subject.is_forward)
  and length(body.previous_threads) > 0
  and (length(headers.references) > 0 or headers.in_reply_to is not null)
)
// negate benign newsletters that mention cyber extortion
and not (
  any(body.links,
      strings.icontains(.display_text, "unsubscribe")
      and strings.icontains(.href_url.path, "unsubscribe")
  )
  // newsletters are typically longer than the average extortion script
  and length(body.current_thread.text) > 2000
)
and length(body.current_thread.text) < 8000
// negate highly trusted sender domains unless they fail DMARC authentication
and (
  (
    sender.email.domain.root_domain in $high_trust_sender_root_domains
    and not headers.auth_summary.dmarc.pass
  )
  or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)

Field Validations

Loading…

Comments (0)

Loading comments...