Potential Fake Instance Of Hxtsr.EXE Executed

Hunt Hypothesis

HxTsr.exe is a Microsoft compressed executable file called Microsoft Outlook Communications. HxTsr.exe is part of Outlook apps, because it resides in a hidden “WindowsApps” subfolder of “C:\Program Fi

Detection Rule

Sigma (Original)

title: Potential Fake Instance Of Hxtsr.EXE Executed
id: 4e762605-34a8-406d-b72e-c1a089313320
status: test
description: |
    HxTsr.exe is a Microsoft compressed executable file called Microsoft Outlook Communications.
    HxTsr.exe is part of Outlook apps, because it resides in a hidden "WindowsApps" subfolder of "C:\Program Files".
    Any instances of hxtsr.exe not in this folder may be malware camouflaging itself as HxTsr.exe
references:
    - Internal Research
author: Sreeman
date: 2020-04-17
modified: 2024-02-08
tags:
    - attack.stealth
    - attack.t1036
logsource:
    product: windows
    category: process_creation
detection:
    # TODO: Link this to the more generic system process rule
    selection:
        Image|endswith: '\hxtsr.exe'
    filter_main_hxtsr:
        Image|contains: ':\program files\windowsapps\microsoft.windowscommunicationsapps_'
        Image|endswith: '\hxtsr.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where TargetProcessName endswith "\\hxtsr.exe" and (not((TargetProcessName contains ":\\program files\\windowsapps\\microsoft.windowscommunicationsapps_" and TargetProcessName endswith "\\hxtsr.exe")))

Required Data Sources

False Positive Guidance

• Unknown

MITRE ATT&CK Context

• Technique: T1036 — T1036

References

• Internal Research
• SigmaHQ Rule