Sublime Security medium experimental mql

Callback phishing via Zoho service abuse

Callback phishing campaigns have been observed abusing Zoho Invoice services to send fraudulent invoices with callback phishing contents.

View Source

Detection Logic

type.inbound

// Legitimate Zoho sending infratructure
and (
  sender.email.domain.root_domain in ('zohoinvoice.com')
  // check for SPF or DMARC passed
  and (headers.auth_summary.spf.pass or headers.auth_summary.dmarc.pass)
)
and (
  // Callback Phishing in body (brand names required)
  (
    length(attachments) == 0

    // brand names are required.
    and regex.icontains(body.current_thread.text,
                        (
                          "mcafee
| norton
| geek.{0,5}squad
| paypal
| ebay
| symantec
| best buy
| lifelock"
                        )
    )
    and 3 of (
      strings.ilike(body.current_thread.text, '*purchase*'),
      strings.ilike(body.current_thread.text, '*payment*'),
      strings.ilike(body.current_thread.text, '*transaction*'),
      strings.ilike(body.current_thread.text, '*subscription*'),
      strings.ilike(body.current_thread.text, '*antivirus*'),
      strings.ilike(body.current_thread.text, '*order*'),
      strings.ilike(body.current_thread.text, '*support*'),
      strings.ilike(body.current_thread.text, '*help line*'),
      strings.ilike(body.current_thread.text, '*receipt*'),
      strings.ilike(body.current_thread.text, '*invoice*'),
      strings.ilike(body.current_thread.text, '*call*'),
      strings.ilike(body.current_thread.text, '*cancel*'),
      strings.ilike(body.current_thread.text, '*renew*'),
      strings.ilike(body.current_thread.text, '*refund*')
    )
    // phone number regex
    and any([body.current_thread.text, subject.subject],
            regex.icontains(., '\b\+?(\d{1}.)?\(?\d{3}?\)?.\d{3}.?\d{4}\b')
    )
  )
  // all attachments are PDFs with callback phishing indicators Brands Required
  or (
    length(attachments) < 3
    and all(attachments, .file_extension == "pdf")
    // the attachment is a pdf with 1 page, and at least 60 ocr chars
    and any(attachments,
            (
              .file_extension == "pdf"
              and any(file.explode(.), .scan.exiftool.page_count < 3)
              and any(file.explode(.), length(.scan.ocr.raw) > 60)

              // 4 of the following strings are found        
              and (
                any(file.explode(.),
                    4 of (
                      strings.icontains(.scan.ocr.raw, "purchase"),
                      strings.icontains(.scan.ocr.raw, "payment"),
                      strings.icontains(.scan.ocr.raw, "transaction"),
                      strings.icontains(.scan.ocr.raw, "subscription"),
                      strings.icontains(.scan.ocr.raw, "antivirus"),
                      strings.icontains(.scan.ocr.raw, "order"),
                      strings.icontains(.scan.ocr.raw, "support"),
                      strings.icontains(.scan.ocr.raw, "help line"),
                      strings.icontains(.scan.ocr.raw, "receipt"),
                      strings.icontains(.scan.ocr.raw, "invoice"),
                      strings.icontains(.scan.ocr.raw, "call"),
                      strings.icontains(.scan.ocr.raw, "helpdesk"),
                      strings.icontains(.scan.ocr.raw, "cancel"),
                      strings.icontains(.scan.ocr.raw, "renew"),
                      strings.icontains(.scan.ocr.raw, "refund"),
                      strings.icontains(.scan.ocr.raw, "amount"),
                      strings.icontains(.scan.ocr.raw, "crypto"),
                      strings.icontains(.scan.ocr.raw, "wallet address"),
                      regex.icontains(.scan.ocr.raw, '\$\d{3}\.\d{2}\b'),
                      regex.icontains(.scan.ocr.raw,
                                      '(\+\d
| 1.(\()?\d{3}(\))?\D\d{3}\D\d{4})'
                      ),
                      regex.icontains(.scan.ocr.raw,
                                      '\+?(\d{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}\d{3}[\s\.\-⋅]{0,5}\d{4}'
                      )
                    )

                    // 1 of the following strings is found, representing common Callback brands          
                    and (
                      1 of (
                        strings.icontains(.scan.ocr.raw, "geek squad"),
                        strings.icontains(.scan.ocr.raw, "lifelock"),
                        strings.icontains(.scan.ocr.raw, "best buy"),
                        strings.icontains(.scan.ocr.raw, "mcafee"),
                        strings.icontains(.scan.ocr.raw, "norton"),
                        strings.icontains(.scan.ocr.raw, "ebay"),
                        strings.icontains(.scan.ocr.raw, "paypal"),
                      )
                      // add additional logic for common language for paypal, which is a valid payment method
                      and not regex.icontains(.scan.ocr.raw,
                                              "paypal[^\n]+accepted"
                      )
                      and not regex.icontains(.scan.ocr.raw,
                                              "payment.{0,30}(via
| by) paypal"
                      )
                      and not regex.icontains(.scan.ocr.raw,
                                              '\d{2,4} norton'
                      ) // an address, example: 1234 Norton Road
                    )
                )
                or any(ml.logo_detect(.).brands,
                       .name in ("PayPal", "Norton", "GeekSquad", "Ebay")
                )
              )
            )
    )
  )
)

Field Validations

Loading…

Comments (0)

Loading comments...