sublimehighRule

Attachment: Archive containing HTML file with file scheme link

Attached archive contains an HTML file with a file:// link, likely pointing to an SMB server. This technique can be used to steal NTLM hashes of users who open the HTML file. Known technique of TA577.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027 T1190 T1203

defense-evasionexecutioninitial-access

Detection Query

type.inbound
and any(attachments,
        .file_extension in $file_extensions_common_archives
        and any(file.explode(.),
                (
                  .file_extension in~ ("html", "htm", "shtml", "dhtml")
                  or .flavors.mime == "text/html"
                  or any(.flavors.yara, . == "html_file")
                )
                and any(.scan.url.urls, .scheme == "file")
        )
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

References

https://www.bleepingcomputer.com/news/security/hackers-steal-windows-ntlm-authentication-hashes-in-phishing-attacks/

Raw Content

name: "Attachment: Archive containing HTML file with file scheme link"
description: "Attached archive contains an HTML file with a file:// link, likely pointing to an SMB server. This technique can be used to steal NTLM hashes of users who open the HTML file. Known technique of TA577."
references:
  - "https://www.bleepingcomputer.com/news/security/hackers-steal-windows-ntlm-authentication-hashes-in-phishing-attacks/"
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          .file_extension in $file_extensions_common_archives
          and any(file.explode(.),
                  (
                    .file_extension in~ ("html", "htm", "shtml", "dhtml")
                    or .flavors.mime == "text/html"
                    or any(.flavors.yara, . == "html_file")
                  )
                  and any(.scan.url.urls, .scheme == "file")
          )
  )
  and (
    not profile.by_sender().solicited
    or (
      profile.by_sender().any_messages_malicious_or_spam
      and not profile.by_sender().any_messages_benign
    )
  )

attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
  - "Exploit"
  - "HTML smuggling"
  - "Social engineering"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "HTML analysis"
id: "edf6d0d9-7d8e-5787-8467-7ca8b61a1b4c"