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PUA.Win32.OfferCore.AN

June 01, 2023
 Analysis by: Francesca Villasanta
 ALIASES:

UDS:Downloader.Win32.Agentb.a (KASPERSKY); Win32/OfferCore.F (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Potentially Unwanted Application

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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.

  TECHNICAL DETAILS

File Size:

1,734,816 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

31 May 2023

Payload:

Drops files, Connects to URLs/IPs

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.

Installation

This Potentially Unwanted Application drops the following files:

  • %User Temp%\is-{Random}.tmp\{filename}.tmp
  • %User Temp%\is-{Random}.tmp\is-{Random}.tmp
  • %User Temp%\is-{Random}.tmp\file_.tmp
  • %User Temp%\is-{Random}.tmp\botva2.dll
  • %User Temp%\is-{Random}.tmp\Helper.dll
  • %User Temp%\is-{Random}.tmp\file_.exe

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • "%User Temp%\is-{Random}.tmp\{filename}.tmp" /SL5="$240142,831488,831488,{Malware Filepath}\{filename}.exe"
  • "%User Temp%\is-{Random}.tmp\file_.exe" /LANG=en /NA=Rh85hR64
  • "%User Temp%\is-{Random}.tmp\file_.tmp" /SL5="$1100E4,1559708,780800,%User Temp%\is-{Random}.tmp\file_.exe" /LANG=en /NA=Rh85hR64

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %User Temp%\is-{Random}.tmp
  • %User Temp%\is-{Random}.tmp\_isetup

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Potentially Unwanted Application connects to the following possibly malicious URL:

  • https://{BLOCKED}ifddppqn.cloudfront.net/installer/60426659/3747246517841079684

  SOLUTION

Minimum Scan Engine:

9.800

SSAPI PATTERN File:

2.627.00

SSAPI PATTERN Date:

01 Jun 2023

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

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.  
  • %User Temp%\is-{Random}.tmp\{filename}.tmp
  • %User Temp%\is-{Random}.tmp\is-{Random}.tmp
  • %User Temp%\is-{Random}.tmp\file_.tmp
  • %User Temp%\is-{Random}.tmp\botva2.dll
  • %User Temp%\is-{Random}.tmp\Helper.dll
  • %User Temp%\is-{Random}.tmp\file_.exe

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\is-{Random}.tmp
  • %User Temp%\is-{Random}.tmp\_isetup

Step 5

Scan your computer with your Trend Micro product to delete files detected as PUA.Win32.OfferCore.AN. 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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