diff --git a/detection-rules/body_self_sender_bold_pdf_link.yml b/detection-rules/body_self_sender_bold_pdf_link.yml new file mode 100644 index 00000000000..b439fc54d7e --- /dev/null +++ b/detection-rules/body_self_sender_bold_pdf_link.yml @@ -0,0 +1,37 @@ +name: "Link: Self-sent PDF lure with subject correlation" +description: "Detects messages sent from a user to themselves containing bold PDF links where the link text correlates with the subject line or sender domain, potentially indicating a compromised account or social engineering technique." +type: "rule" +severity: "medium" +source: | + type.inbound + // self sender + and ( + length(recipients.to) == 1 + and recipients.to[0].email.email == sender.email.email + ) + // bold a tags ending in PDF + and any(html.xpath(body.html, '//a[./b]').nodes, + strings.iends_with(.display_text, ".pdf") + and ( + // subject appears as the .pdf link + any(regex.extract(subject.base, '(?P\w+)'), + strings.contains(..display_text, .named_groups["word"]) + ) + // OR sender domain appears as the pdf link + or strings.icontains(.display_text, sender.email.domain.sld) + ) + and coalesce(strings.parse_url(.display_text).scheme, "not_url") == "not_url" + ) + +attack_types: + - "BEC/Fraud" + - "Credential Phishing" +tactics_and_techniques: + - "Social engineering" + - "Evasion" +detection_methods: + - "Header analysis" + - "HTML analysis" + - "Sender analysis" + - "Content analysis" +id: "a902702f-0e69-57dd-af81-08225218cffb"