• Sublime Core Feed
Medium Severity

Business Email Compromise (BEC) attempt from untrusted sender (French/Français)

Description

Detects potential Business Email Compromise (BEC) attacks by searching for common French BEC language within the email body from first-time senders.

References

No references.

Sublime Security
Created Nov 14th, 2024 • Last updated Jul 16th, 2025
Source
type.inbound
and length(body.links) == 0
and ml.nlu_classifier(body.current_thread.text).language == "french"
and 1 of (
  regex.icontains(subject.subject,
                  '(mise (a|à) jour|changé|changement).{0,20}(bancaire|de banque)'
  ),
  regex.icontains(body.current_thread.text,
                  '(changement|changé) de (banque)|changement bancaire|coordonnées.{0,20}(compte|banque|bancaire|salaire)',
  ),
  (regex.icontains(body.current_thread.text, 'parler.{0,20}confiance'))
)
// negating legit replies
and not (
  (
    strings.istarts_with(subject.subject, "RE:")
    // out of office auto-reply
    // the NLU model will handle these better natively soon
    or strings.istarts_with(subject.subject, "Automatic reply:")
    or regex.imatch(subject.subject,
                    '(\[[^\]]+\]\s?){0,3}(re|fwd?|automat.*)\s?:.*'
    )
  )
  and (
    length(headers.references) > 0
    or any(headers.hops, any(.fields, strings.ilike(.name, "In-Reply-To")))
  )
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)

// negate highly trusted sender domains unless they fail DMARC authentication
and (
  (
    sender.email.domain.root_domain in $high_trust_sender_root_domains
    and not headers.auth_summary.dmarc.pass
  )
  or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)
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