• Sublime Core Feed
Medium Severity

BEC/Fraud - Job Scam Fake thread or plaintext pivot to freemail

Labels

BEC/Fraud
Free email provider
Out of band pivot
Content analysis
File analysis
Natural Language Understanding

Description

Detects potential job scams using plaintext or fake threads attempting to pivot to a freemail address from an unsolicited sender.

References

No references.

Sublime Security
Created Jan 8th, 2024 • Last updated Jan 8th, 2024
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and any(ml.nlu_classifier(body.current_thread.text).entities,
        .name in ("greeting", "salutation")
)

// most likely to occur in plain text
and (
  body.html.raw is null
  or 

  // HTML is not null but fake thread
  (
    strings.istarts_with(subject.subject, "RE:")
    or strings.istarts_with(subject.subject, "FWD:")
  )
  and (
    (length(headers.references) == 0 and headers.in_reply_to is null)
    or not any(headers.hops, any(.fields, strings.ilike(.name, "In-Reply-To")))
  )
)
and 3 of (
  any([subject.subject, body.current_thread.text],
      regex.icontains(., '(full|part).time')
  ),
  strings.ilike(body.current_thread.text, '*job*'),
  regex.icontains(body.current_thread.text, '\bHR\b'),
  strings.ilike(body.current_thread.text, '*manager*'),
  strings.ilike(body.current_thread.text, '*commission*'),
  strings.ilike(body.current_thread.text, '*hourly*'),
  strings.ilike(body.current_thread.text, '*prior experience*'),
  strings.ilike(body.current_thread.text, '*company rep*'),
  strings.ilike(body.current_thread.text, "100% legal")
)

// all attachments are images or there's no attachments
and (
  (
    length(attachments) > 0
    and all(attachments, .file_type in $file_types_images)
  )
  or length(attachments) == 0
)

// there's an email in the body
and regex.contains(body.current_thread.text,
                   "[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}"
)

// and it's likely a freemail
and any($free_email_providers, strings.icontains(body.current_thread.text, .))

// and that email doesn't match the sender domain
and (
  all(body.links, .href_url.domain.root_domain != sender.email.domain.domain)
  or sender.email.domain.root_domain in $free_email_providers
)
and (
  (
    not profile.by_sender().solicited
    and not profile.by_sender().any_false_positives
  )
  or profile.by_sender().any_messages_malicious_or_spam
)
and not profile.by_sender().any_false_positives
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