• Sublime Core Feed
Medium Severity

Reconnaissance: Hotel booking reply-to redirect

Description

Detects messages impersonating hotel booking inquiries by identifying common hotel-related language patterns from senders where the reply-to is a free email provider and differs from the sender domain in an effort to validate whether a recipient address is valid or not, potentially preceding an attack.

References

No references.

Sublime Security
Created Jan 27th, 2026 • Last updated Jan 27th, 2026
Source
type.inbound
and any(headers.reply_to,
        .email.domain.root_domain in $free_email_providers
        and .email.domain.root_domain != sender.email.domain.root_domain
)
and all(recipients.to,
        .email.domain.root_domain != sender.email.domain.root_domain
)
and length(body.links) == 0
and length(attachments) == 0
and length(body.current_thread.text) < 600
and not (
  (subject.is_reply or subject.is_forward)
  and (length(headers.references) > 0 or headers.in_reply_to is not null)
)
and (
  (
    strings.ilike(body.current_thread.text,
                  '*hotel*',
                  '*your property*',
                  '*accommodation*',
                  '*guest services*',
                  '*reception*',
                  '*front desk*'
    )
    and strings.ilike(body.current_thread.text,
                      '*booking*',
                      '*to book*',
                      '*book a *',
                      '*reserv*',
                      '*room*',
                      '*suite*',
                      '*availability*',
                      '*check-in*',
                      '*available dates*',
                      '*family trip*',
                      '*deluxe accommodation*',
                      '*two children*',
                      '*hotel manager*'
    )
  )
  or strings.ilike(subject.base,
                   '*hotel*',
                   '*room reserv*',
                   '*room inquiry*',
                   '*room availability*',
                   '*suite*',
                   '*accommodation*'
  )
)
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