Analysis by: Noel Anthony Llimos
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 SYSTEM IMPACT RATING:
 INFORMATION EXPOSURE:

  • Threat Type: Potentially Unwanted Application

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This Potentially Unwanted Application arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be manually installed by a user.

  TECHNICAL DETAILS

File Size: 2,171,904 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 11 Mar 2019

Arrival Details

This Potentially Unwanted Application arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It may be manually installed by a user.

Installation

This Potentially Unwanted Application drops the following files:

  • %User Temp%\HFS last update check.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • HttpFileServer

Other System Modifications

This Potentially Unwanted Application adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
*\shell\Add to HFS\
command
(Default) = "%User Temp%\{Executed File Name}.exe" "%1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Folder\shell\Add to HFS\
command
(Default) = "%User Temp%\{Executed File Name}.exe" "%1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.vfs
(Default) = HFS file system

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.vfs\shell\Open\
command
(Default) = "%User Temp%\{Executed File Name}.exe" "%1"

HKEY_CURRENT_USER\Software\rejetto\
HFS
(Default) = HFS 2.3m - Build #300 active=yes only-1-instance=yes window=293,219,1092,648 window-max=no easy=yes port= files-box-ratio=0 log-max-lines=2000 log-read-only=yes log-file-name= log-font-name= log-font-size=0 log-date=no log-time=yes log-to-screen=yes log-only-served=yes log-server-start=no log-server-stop=no log-connections=no log-disconnections=no log-bytes-sent=no log-bytes-received=no log-replies=no log-requests=yes log-uploads=yes log-deletions=yes log-full-downloads=yes log-d

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 2.153.00
FIRST VSAPI PATTERN DATE: 06 Mar 2019
VSAPI OPR PATTERN File: 2.153.00
VSAPI OPR PATTERN Date: 06 Mar 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\*\shell\Add to HFS\command
    • (Default) = "%User Temp%\{Executed File Name}.exe" "%1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Folder\shell\Add to HFS\command
    • (Default) = "%User Temp%\{Executed File Name}.exe" "%1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.vfs
    • (Default) = HFS file system
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.vfs\shell\Open\command
    • (Default) = "%User Temp%\{Executed File Name}.exe" "%1"
  • In HKEY_CURRENT_USER\Software\rejetto\HFS
    • (Default) = HFS 2.3m - Build #300 active=yes only-1-instance=yes window=293,219,1092,648 window-max=no easy=yes port= files-box-ratio=0 log-max-lines=2000 log-read-only=yes log-file-name= log-font-name= log-font-size=0 log-date=no log-time=yes log-to-screen=yes log-only-served=yes log-server-start=no log-server-stop=no log-connections=no log-disconnections=no log-bytes-sent=no log-bytes-received=no log-replies=no log-requests=yes log-uploads=yes log-deletions=yes log-full-downloads=yes log-d

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.

Step 5

Scan your computer with your Trend Micro product to delete files detected as PUA.Win32.HFileServer.AA. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:


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