• Sublime Core Feed
High Severity

Attachment: HTML smuggling - QR Code with suspicious links

Labels

Credential Phishing
QR code
Computer Vision
Header analysis
Natural Language Understanding
QR code analysis
Sender analysis
URL analysis
URL screenshot

Description

This rule detects messages with HTML attachments containing QR codes

References

No references.

Sublime Security
Created Nov 22nd, 2023 • Last updated Apr 25th, 2024
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and 1 <= length(attachments) < 3

// inspects HTML attachments for QR codes
and any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml", "xhtml")
          or (
            .file_extension is null
            and .file_type == "unknown"
            and .content_type == "application/octet-stream"
          )
          or .file_extension in~ $file_extensions_common_archives
          or .file_type == "html"
          or .content_type == "text/html"
        )
        and any(file.explode(file.html_screenshot(.)),
                // any URL
                ml.link_analysis(.scan.qr.url).submitted
                // currently we won't pick it up as a URL if it's
                // not prefaced with a scheme. this is not very strong,
                // but it's unlikely to cause FPs for this rule
                or regex.contains(.scan.qr.data, '\.')
        )
)

// 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
)

and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_false_positives
  )
)
and not profile.by_sender().any_false_positives
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