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High Severity

Extortion / Sextortion - PDF attachment leveraging breach data from freemail sender

Description

Detects sextortion attempts leveraging breach data, including names, addresses, phone numbers and frequently using Google Maps/Bing Maps streetview images to bolster confidence and fear.

References

No references.

Sublime Security
Created Sep 12th, 2024 • Last updated Feb 3rd, 2025
Source
type.inbound

// sender is a freemail domain
and sender.email.domain.root_domain in $free_email_providers

// attachment filename is the same as the subject
and any(attachments,
        (
          strings.ilevenshtein(strings.concat(subject.subject,
                                              ".",
                                              .file_extension
                               ),
                               .file_name
          ) <= 1
        )
        or strings.contains(.file_name, subject.subject)
)

// body contains a US address, or the body is the subject
and (
  regex.icontains(body.current_thread.text,
                  '\d+\s[\w\s.]+(?:\n)?[\w\s]+\s[A-Z]{2}\s\d{5}(?:-\d{4})?(?:\n)?|\d+\s[\w\s.]+(?:Street|St|Avenue|Ave|Boulevard|Blvd|Road|Rd|Drive|Dr|Lane|Ln|Court|Ct|Way|Place|Pl|Terrace|Ter|Circle|Cir|Parkway|Pkwy|Trail|Trl|Highway|Hwy|Loop)\b\.?',
                  // a Canadian address
                  '\d+\s[\w\s.]+(?:\n)?[\w\s]+\s((?:Ontario|ON)|(?:Quebec|QC)|(?:Nova Scotia|NS)|(?:New Brunswick|NB)|(?:Manitoba|MB)|(?:British Columbia|BC)|(?:Prince Edward Island|PEI?)|(?:Saskatchewan|SK)|(?:Alberta|AB)|(?:Newfoundland and Labrador|NL)|(?:Yukon|YT)|(?:Northwest Territories|NT)|(?:Nunavut|NU))\s*[ABCEGHJ-NPRSTVXY]\d[ABCEGHJ-NPRSTV-Z][ -]?\d[ABCEGHJ-NPRSTV-Z]\d'
  )
  or subject.subject == body.current_thread.text
)

// there's a PDF attachment with an image at a depth of one, measuring 148x148 and containing a QR code that is a BTC address
and any(attachments,
        .file_type == "pdf"
        and any(file.explode(.),
                (
                  (.depth == 1 and .flavors.mime == "image/jpeg")
                  and (
                    .scan.exiftool.image_height == 148
                    and .scan.exiftool.image_width == 148
                    and regex.match(.scan.qr.data,
                                    '(1[a-km-zA-HJ-NP-Z1-9]{25,34}|3[a-km-zA-HJ-NP-Z1-9]{25,34}|bc1[qp-z0-9]{39,59})'
                    )
                  )
                )
                or (
                  any(.scan.strings.strings,
                      regex.icontains(.,
                                      'Amount(?:\s*\w+){0,3}\s*:?\s*(?:USD\s*)?(?:\$\s?\d+|\d+\s?\$?)'
                      )
                  )
                  and any(.scan.strings.strings,
                          regex.icontains(.,
                                          '(\bBITCOIN\b|\bBTC\b|\bLTC\b|Wallet)'
                          )
                  )
                )
        )
)
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