Description

Detects inbound messages with empty subjects impersonating a secure email portal, identified through multiple indicators including hidden HTML characters used to obfuscate the sender address, recipient domain echoed back as a portal sender, template typos, or frozen tracking links associated with known secure messaging infrastructure abuse.

References

No references.

Sublime Security
Created Jun 18th, 2026 • Last updated Jun 18th, 2026
Source
type.inbound
and subject.base == ""
and strings.icontains(body.current_thread.text, "Secure Emails")
and strings.icontains(body.current_thread.text, "Title:")
and (
  // hidden-@ HTML obfuscation
  regex.icontains(body.html.raw, '<font[^>]+display\s*:\s*none[^>]*>@</font>')
  // recipient root domain echoed back as a portal sender
  or any(recipients.to,
         strings.icontains(body.current_thread.text,
                           strings.concat("acts@", .email.domain.root_domain)
         )
  )
  // template typo
  or strings.icontains(body.current_thread.text, "commuication portal")
  // frozen crId or linkprotect.cudasvc.com inner target
  or any(body.links,
         .href_url.domain.domain == "links.us1.defend.egress.com"
         and (
           strings.icontains(.href_url.query_params,
                             "crId=6a17340ad2523c97775fed21"
           )
           or strings.icontains(.href_url.query_params,
                                "OriginalLink=linkprotect.cudasvc.com"
           )
         )
  )
)
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