Suspicious File Drop by Exchange — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-10-04 / not supplied.

{
  "product": "windows",
  "category": "file_event"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 4382699949ea9d9d8c850fe0cbffe0d0164f5372afa2f5611ca7f436a8648f02

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious File Drop by Exchange
id: 6b269392-9eba-40b5-acb6-55c882b20ba6
related:
    - id: bd1212e5-78da-431e-95fa-c58e3237a8e6
      type: similar
status: test
description: Detects suspicious file type dropped by an Exchange component in IIS
references:
    - https://www.microsoft.com/security/blog/2022/09/30/analyzing-attacks-using-the-exchange-vulnerabilities-cve-2022-41040-and-cve-2022-41082/
    - https://www.gteltsc.vn/blog/canh-bao-chien-dich-tan-cong-su-dung-lo-hong-zero-day-tren-microsoft-exchange-server-12714.html
    - https://en.gteltsc.vn/blog/cap-nhat-nhe-ve-lo-hong-bao-mat-0day-microsoft-exchange-dang-duoc-su-dung-de-tan-cong-cac-to-chuc-tai-viet-nam-9685.html
author: Florian Roth (Nextron Systems)
date: 2022-10-04
tags:
    - attack.persistence
    - attack.t1190
    - attack.initial-access
    - attack.t1505.003
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\w3wp.exe'
        CommandLine|contains: 'MSExchange'
    selection_types:
        TargetFilename|endswith:
            - '.aspx'
            - '.asp'
            - '.ashx'
            - '.ps1'
            - '.bat'
            - '.exe'
            - '.dll'
            - '.vbs'
    condition: all of selection*
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://www.microsoft.com/security/blog/2022/09/30/analyzing-attacks-using-the-exchange-vulnerabilities-cve-2022-41040-and-cve-2022-41082/
• https://www.gteltsc.vn/blog/canh-bao-chien-dich-tan-cong-su-dung-lo-hong-zero-day-tren-microsoft-exchange-server-12714.html
• https://en.gteltsc.vn/blog/cap-nhat-nhe-ve-lo-hong-bao-mat-0day-microsoft-exchange-dang-duoc-su-dung-de-tan-cong-cac-to-chuc-tai-viet-nam-9685.html