diff --git a/detection-rules/callback_phishing_nlu_body_or_attachments.yml b/detection-rules/callback_phishing_nlu_body_or_attachments.yml new file mode 100644 index 00000000000..e45ba323222 --- /dev/null +++ b/detection-rules/callback_phishing_nlu_body_or_attachments.yml @@ -0,0 +1,61 @@ +name: "Callback Phishing NLU body or attachment from first-time sender" +description: | + Detects callback scams by analyzing text within images of receipts or invoices from first time senders. +type: "rule" +severity: "medium" +source: | + type.inbound + and length(attachments) < 5 + and ( + any(attachments, + (.file_type in $file_types_images or .file_type == "pdf") + and any(file.explode(.), + + // exclude images taken with mobile cameras and screenshots from android + not any(.scan.exiftool.fields, + .key == "Model" + or .key == "Software" and strings.starts_with(.value, "Android") + ) + and any(ml.nlu_classifier(.scan.ocr.raw).intents, + .name == "callback_scam" and .confidence == "high" + ) + ) + ) + or any(ml.nlu_classifier(body.current_thread.text).intents, + .name in ("callback_scam") + and .confidence == "high" + and length(body.current_thread.text) < 1500 + ) + ) + and not ( + any(headers.domains, .domain == "smtp-out.gcp.bigcommerce.net") + and strings.icontains(body.html.raw, "bigcommerce.com") + ) + + // negate highly trusted sender domains unless they fail DMARC authentication + and + ( + ( + sender.email.domain.root_domain in $high_trust_sender_root_domains + and ( + any(distinct(headers.hops, .authentication_results.dmarc is not null), + strings.ilike(.authentication_results.dmarc, "*fail") + ) + ) + ) + or sender.email.domain.root_domain not in $high_trust_sender_root_domains + ) +attack_types: + - "Callback Phishing" +tactics_and_techniques: + - "Out of band pivot" + - "Social engineering" +detection_methods: + - "Content analysis" + - "File analysis" + - "Optical Character Recognition" + - "Natural Language Understanding" + - "Sender analysis" +id: "b93c6f94-c9a3-587a-8eb5-6856754f8222" +testing_pr: 931 +testing_sha: 2931bf7121ac1c3637094921a3432f8b4bb948a1