Service abuse: FlipHTML5 with attachment deception and credential theft language

calendar Oct 30, 2025  ·
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Detects messages that reference attachments without including any, contain links to FlipHTML5 services, and exhibit high-confidence credential theft language patterns.

Sublime rule (View on GitHub)

 1name: "Service abuse: FlipHTML5 with attachment deception and credential theft language"
 2description: "Detects messages that reference attachments without including any, contain links to FlipHTML5 services, and exhibit high-confidence credential theft language patterns."
 3type: "rule"
 4severity: "medium"
 5source: |
 6  type.inbound
 7  // messages contain wording to "see attached" but contains no attachments
 8  and (
 9    regex.icontains(body.current_thread.text,
10                    "attached|see.*attached|find.*attached|please{0,10}attached"
11    )
12    and length(attachments) == 0
13  )
14  // and the link goes to fliphtml5 and contains suspect "click me" language
15  and any(body.links,
16          .href_url.domain.root_domain == "fliphtml5.com"
17  )
18  // and we have confidence its cred theft
19  and any(ml.nlu_classifier(body.current_thread.text).intents,
20          .name == "cred_theft" and .confidence != "low"
21  )  
22
23attack_types:
24  - "Credential Phishing"
25tactics_and_techniques:
26  - "Social engineering"
27  - "Free file host"
28  - "Evasion"
29detection_methods:
30  - "Content analysis"
31  - "Natural Language Understanding"
32  - "URL analysis"
33id: "02464799-4c4c-58e0-936f-41d8bcd7b276"
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