• Sublime Core Feed
Medium Severity

Callback Phishing: Branded invoice from sender/reply-to domain less than 30 days old

Labels

Callback Phishing
Impersonation: Brand
Out of band pivot
Social engineering
Header analysis
Natural Language Understanding
Optical Character Recognition
Whois

Description

This rule checks for invoicing content from a sender, reply-to domain or return-path domain less than 30d old. It also checks the body or the OCR'd screenshot for key words commonly abused in fraudulent invoicing attacks.

References

No references.

Sublime Security
Created Nov 20th, 2023 • Last updated Apr 25th, 2024
Feed Source
Sublime Core Feed
Source
GitHub

type.inbound
// reply to domain that's less than 30d old and doesn't match the sender
and (
  (
    length(headers.reply_to) > 0
    and all(headers.reply_to,
            network.whois(.email.domain).days_old <= 30
            and .email.email != sender.email.email
    )
  )

  // or the return path or sender domain is less than 30d old 
  or network.whois(headers.return_path.domain).days_old <= 30
  or network.whois(sender.email.domain).days_old <= 30
)

// invoicing with high confidence
and any(ml.nlu_classifier(body.current_thread.text).tags,
        .name == "invoice" and .confidence == "high"
)

// commonly abused brands in body
and (
  strings.ilike(body.current_thread.text,
                "*mcafee*",
                "*norton*",
                "*geek squad*",
                "*paypal*",
                "*ebay*",
                "*symantec*",
                "*best buy*",
                "*lifelock*",
                "*virus*"
  )

  // commonly abused brand logo
  or any(ml.logo_detect(beta.message_screenshot()).brands,
         .name in ("PayPal", "Norton", "GeekSquad", "Ebay")
  )

  // check message screenshot ocr for commonly abused brands
  or any(file.explode(beta.message_screenshot()),
         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"),
           strings.icontains(.scan.ocr.raw, "virus"),
         )
  )
)

// phone number regex
and regex.icontains(body.current_thread.text,
                    '\+?(\d{1}.)?\(?\d{3}?\)?.\d{3}.?\d{4}'
)
and not profile.by_sender().solicited
and not profile.by_sender().any_false_positives
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