Sublime Security medium experimental mql

Service abuse: Formester with suspicious link behavior

Detects abuse of the Formester form service where links either redirect to credential phishing pages, contain suspicious top-level domains in the final DOM and/or redirect history, or display 'secure message' text indicating potential credential theft.

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Detection Logic

type.inbound
// LA invokes page first before scanning additional links.
and (
  any(filter(body.links, .href_url.domain.root_domain == 'formester.com'),
      (
        ml.link_analysis(., mode="aggressive").credphish.disposition == "phishing"
      )
      // any links in the final dom lead to a suspicious tld.
      or any(ml.link_analysis(.).final_dom.links,
             .href_url.domain.tld in $suspicious_tlds
             or ml.link_analysis(.href_url).effective_url.domain.tld in $suspicious_tlds
      )

      // link redirects to a suspicious TLD.
      or any(ml.link_analysis(., mode="aggressive").redirect_history,
             .domain.tld in $suspicious_tlds
      )
      // suspicious landing verbiage. Keywords can be expanded.
      or strings.icontains(ml.link_analysis(., mode="aggressive").final_dom.display_text,
                           "secure message"
      )
      // suspicious link verbiage.
      or regex.icontains(.display_text,
                         "(view
| show
| download).{0,20}(Doc(ument)?(s)?
| files(s)?
| attached)"
      )
  )
  // suspicious keywords/phrasing in body.
  or (
    any(body.links, .href_url.domain.root_domain == 'formester.com')
    and strings.icontains(body.current_thread.text,
                          "use of Microsoft 365 and may contain content"
    )
  )
)

Field Validations

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