• Sublime Core Feed
Medium Severity

Callback Phishing in body or attachment (untrusted sender)

Labels

Description

Detects callback scams by analyzing text within images of receipts or invoices from untrusted senders.

References

No references.

Sublime Security
Created Aug 17th, 2023 • Last updated Feb 12th, 2024
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and length(attachments) < 5
and (
  any(attachments,
      (.file_type in $file_types_images or .file_type == "pdf")
      and any(file.explode(.),

              // exclude images taken with mobile cameras and screenshots from android
              not any(.scan.exiftool.fields,
                      .key == "Model"
                      or (
                        .key == "Software"
                        and strings.starts_with(.value, "Android")
                      )
                      or (.key == "UserComment" and .value == "Screenshot")
              )
              and any(ml.nlu_classifier(.scan.ocr.raw).intents,
                      .name == "callback_scam" and .confidence == "high"
              )
      )
  )
  or any(ml.nlu_classifier(body.current_thread.text).intents,
         .name in ("callback_scam")
         and .confidence == "high"
         and length(body.current_thread.text) < 1500
  )
)
and not (
  any(headers.domains, .domain == "smtp-out.gcp.bigcommerce.net")
  and strings.icontains(body.html.raw, "bigcommerce.com")
)
and (
  (
    profile.by_sender().prevalence in ("new", "outlier")
    and not profile.by_sender().solicited
  )
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_false_positives
  )
)

// negate highly trusted sender domains unless they fail DMARC authentication
and (
  (
    sender.email.domain.root_domain in $high_trust_sender_root_domains
    and (
      any(distinct(headers.hops, .authentication_results.dmarc is not null),
          strings.ilike(.authentication_results.dmarc, "*fail")
      )
    )
  )
  or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)

Playground

Test against your own EMLs or sample data.

Share

Post about this on your socials.

Get Started. Today.

Managed or self-managed. No MX changes.

Get Started