• Sublime Core Feed

Description

This rule examines messages containing image attachments that utilize Google's open redirect (google[.]com/url...). To enhance accuracy and minimize false positives, the rule conducts additional assessments for suspicious indicators, as indicated in the comments.

References

No references.

Sublime Security
Created Aug 17th, 2023 • Last updated Sep 22nd, 2025
Source
type.inbound
// All attachments are images or 0 attachments
and (
  (length(attachments) > 0 and all(attachments, .file_type in $file_types_images))
  or length(attachments) == 0
)
and sender.email.domain.root_domain not in $org_domains
// negate auth'ed google messages
and not (
  sender.email.domain.sld == "google"
  and sender.email.local_part in ("googlealerts-noreply", "comments-noreply")
  and headers.auth_summary.spf.pass
  and headers.auth_summary.dmarc.pass
)
// not a reply
and (
  length(headers.references) == 0
  or not any(headers.hops, any(.fields, strings.ilike(.name, "In-Reply-To")))
)
// With a Google Redirect
and any(body.links,
        (
          .href_url.domain.sld == "google"
          and .href_url.path == "/url"
          and regex.contains(.href_url.query_params, "hl=.{2}&q=http(s)?://")
        )
        or any(.href_url.rewrite.encoders, . == 'google_open_redirect')
)
and 2 of (
  // Not a google logo
  any(attachments,
      .file_type in $file_types_images
      and (
        any(ml.logo_detect(.).brands, not strings.starts_with(.name, "Google"))
        or any(ml.logo_detect(file.message_screenshot()).brands,
               not strings.starts_with(.name, "Google")
        )
      )
  ),
  // Body analysis - NLU - Credential theft
  (
    any(ml.nlu_classifier(body.current_thread.text).intents,
        .name == "cred_theft" and .confidence in~ ("medium", "high")
    )
  ),
  // Image analysis - NLU - Credential theft language
  (
    any(attachments,
        .file_type in $file_types_images
        and any(file.explode(.),
                any(ml.nlu_classifier(.scan.ocr.raw).intents, .name == "cred_theft")
        )
    )
  ),
  // Content analysis - Body - Urgency
  (
    any(ml.nlu_classifier(body.current_thread.text).entities, .name == "urgency")
  ),

  // White font is found in html raw
  (
    length(body.html.display_text) < 500
    and regex.icontains(body.html.raw,
                        '<div style="color: #fff(fff)?.[^<]+<\/div><\/div><\/body><\/html>$'
    )
  )

  // domains using .app matching this pattern observed abusing google's redirect
  or regex.icontains(sender.email.domain.domain, '[a-z]{3,}\.\d{5,}[^\.]+\.app$')
)
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