Service abuse: FileMail callback scam

calendar Jul 24, 2026  ·
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Detects inbound messages from FileMail's no-reply address where the first line of the email body is classified with high confidence as a callback scam using natural language understanding. Attackers leverage legitimate file sharing services to deliver fraudulent messages that instruct recipients to call a phone number, often impersonating tech support or financial institutions.

Sublime rule (View on GitHub)

 1name: "Service abuse: FileMail callback scam"
 2description: "Detects inbound messages from FileMail's no-reply address where the first line of the email body is classified with high confidence as a callback scam using natural language understanding. Attackers leverage legitimate file sharing services to deliver fraudulent messages that instruct recipients to call a phone number, often impersonating tech support or financial institutions."
 3type: "rule"
 4severity: "medium"
 5source: |
 6  type.inbound
 7  and sender.email.email == "no-reply@filemail.com"
 8  and any(ml.nlu_classifier(regex.extract(body.current_thread.text,
 9                                          '^(?P<first_line>[^\n]+)\n'
10                            )[0].named_groups["first_line"]
11          ).intents,
12          .name == "callback_scam" and .confidence == "high"
13  )
14  
15    
16attack_types:
17  - "Callback Phishing"
18tactics_and_techniques:
19  - "Social engineering"
20  - "Free file host"
21  - "Out of band pivot"
22detection_methods:
23  - "Natural Language Understanding"
24  - "Sender analysis"
25  - "Content analysis"
26id: "9305a806-2c58-5bd7-8c96-c8b2b74d9961"
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