sublimemediumRule

Attachment with encrypted zip (unsolicited)

Recursively scans files and archives to detect encrypted zip files.

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1036 T1027 T1573

defense-evasion

Detection Query

type.inbound
and any(attachments,
        (.file_type == "zip" or .file_extension == "zip")
        and any(file.explode(.), any(.flavors.yara, . == 'encrypted_zip'))
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)
and not profile.by_sender().prevalence == "common"

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

References

https://www.zdnet.com/article/this-phishing-email-contains-a-password-protected-file-dont-open-it/

Tags

Attack surface reduction

Raw Content

name: "Attachment with encrypted zip (unsolicited)"
description: |
  Recursively scans files and archives to detect encrypted zip files.
references:
  - "https://www.zdnet.com/article/this-phishing-email-contains-a-password-protected-file-dont-open-it/"
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(attachments,
          (.file_type == "zip" or .file_extension == "zip")
          and any(file.explode(.), any(.flavors.yara, . == 'encrypted_zip'))
  )
  and (
    not profile.by_sender().solicited
    or (
      profile.by_sender().any_messages_malicious_or_spam
      and not profile.by_sender().any_messages_benign
    )
  )
  and not profile.by_sender().prevalence == "common"
tags:
  - "Attack surface reduction"
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "Encryption"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "Sender analysis"
id: "697c87ae-943d-54a0-a41b-ba1667147e03"