Medium Severity
Business Email Compromise (BEC) attempt from untrusted sender
Description
Detects potential Business Email Compromise (BEC) attacks by analyzing text within the email body from first-time senders.
References
No references.
Sublime Security
Created Aug 17th, 2023 • Last updated Jun 24th, 2024
Feed Source
Sublime Core Feed
Source
type.inbound
and any(ml.nlu_classifier(body.current_thread.text).intents,
.name in ("bec") and .confidence == "high"
)
// 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_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 not headers.auth_summary.dmarc.pass
)
or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)
Playground
Test against your own EMLs or sample data.