Attachment: PDF file with low reputation link to ZIP file (unsolicited)

 1name: "Attachment: PDF file with low reputation link to ZIP file (unsolicited)"
 2description: |
 3    Detects messages with PDF attachments linking directly to zip files from unsolicited senders.
 4type: "rule"
 5severity: "medium"
 6authors:
 7  - name: "Michael Tingle"
 8source: |
 9  type.inbound
10  and any(ml.nlu_classifier(body.current_thread.text).entities, .name == "request")
11  and any(attachments,
12          .file_extension == "pdf"
13          and any(file.explode(.),
14                  any(.scan.pdf.urls,
15                      regex.contains(.url, '\.(?:zip)') and .domain.root_domain not in $tranco_1m
16                  )
17          )
18  )
19  and (
20    not profile.by_sender().solicited
21    or (
22      profile.by_sender().any_messages_malicious_or_spam
23      and not profile.by_sender().any_false_positives
24    )
25  )  
26tags:
27  - "Malfam: QakBot"
28attack_types:
29  - "Malware/Ransomware"
30tactics_and_techniques:
31  - "Evasion"
32  - "PDF"
33detection_methods:
34  - "Archive analysis"
35  - "File analysis"
36  - "Natural Language Understanding"
37  - "Sender analysis"
38  - "URL analysis"
39id: "d1ee2859-acd1-5c12-9b74-89439ed1eaf1"