Suspicious MSExchangeMailboxReplication ASPX Write — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: high. Source dates: 2022-02-25 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 588911a89962fc565bbda7631c23cdd2411a913caebbb4554399889232c59016

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 MSExchangeMailboxReplication ASPX Write
id: 7280c9f3-a5af-45d0-916a-bc01cb4151c9
status: test
description: Detects suspicious activity in which the MSExchangeMailboxReplication process writes .asp and .apsx files to disk, which could be a sign of ProxyShell exploitation
references:
    - https://redcanary.com/blog/blackbyte-ransomware/
author: Florian Roth (Nextron Systems)
date: 2022-02-25
tags:
    - attack.initial-access
    - attack.t1190
    - attack.persistence
    - attack.t1505.003
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\MSExchangeMailboxReplication.exe'
        TargetFilename|endswith:
            - '.aspx'
            - '.asp'
    condition: selection
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://redcanary.com/blog/blackbyte-ransomware/