Windows: Detect execution of renamed megasync.exe (original MegaSync) via process creation

Flags process launches where megasync.exe appears under a renamed or nonstandard execution context based on process creation fields.

FreeUnreviewedSigmahighv1

windows-detect-execution-of-renamed-megasync-exe-original-megasync-via-process-c-643bdcac

title: "Windows: Detect execution of renamed megasync.exe (original MegaSync) via process creation"
id: fcaf72ca-3902-4895-8538-739465b53c9d
status: test
description: This rule identifies Windows process creation events where the original file name is megasync.exe but the executed image path ends with \\megasync.exe and the image is not the expected direct megasync.exe execution. Renaming a legitimate executable can help attackers blend in with normal activity while launching the same functionality under a different name. It relies on process creation telemetry, matching OriginalFileName and the Image path ending in the MegaSync executable name.
references:
  - https://redcanary.com/blog/rclone-mega-extortion/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_renamed_megasync.yml
author: Sittikorn S, Huntrule Team
date: 2021-06-22
modified: 2023-02-03
tags:
  - attack.stealth
  - attack.t1218
logsource:
  product: windows
  category: process_creation
detection:
  selection:
    OriginalFileName: megasync.exe
  filter:
    Image|endswith: \megasync.exe
  condition: selection and not filter
falsepositives:
  - Software that illegally integrates MegaSync in a renamed form
  - Administrators that have renamed MegaSync
level: high
license: DRL-1.1
related:
  - id: 643bdcac-8b82-49f4-9fd9-25a90b929f3b
    type: derived

What it detects

This rule identifies Windows process creation events where the original file name is megasync.exe but the executed image path ends with \\megasync.exe and the image is not the expected direct megasync.exe execution. Renaming a legitimate executable can help attackers blend in with normal activity while launching the same functionality under a different name. It relies on process creation telemetry, matching OriginalFileName and the Image path ending in the MegaSync executable name.

Known false positives

Software that illegally integrates MegaSync in a renamed form
Administrators that have renamed MegaSync

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.