TROJ_NYMAIM.YGS


 ALIASES:

Win32/TrojanDownloader.Nymaim.BA trojan (ESET)

 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 is injected into all running processes to remain memory resident.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Apr 2016

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:

  • %User Temp%\{random filename}.{random extension} - encrypted component
  • %All Users Profile%\{random folder name}\{random filename}.{random extension} - encrypted component

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It is injected into all running processes to remain memory resident.

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
LVFP
{random name} = "{encrypted code}"

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • google.com
  • microsoft.com

It connects to the following possibly malicious URL:

  • {domain generated algorithm}.{com,pw,net,in}
    such as the following:
    • {BLOCKED}ozjlsy.in
    • {BLOCKED}hnn.pw
    • {BLOCKED}t.in
    • {BLOCKED}w.com
    • {BLOCKED}fnrydw.com
    • {BLOCKED}orl.net
    • {BLOCKED}vdk.in
    • {BLOCKED}w.pw
    • {BLOCKED}z.com
    • {BLOCKED}o.net
    • {BLOCKED}wkwg.com
    • {BLOCKED}roqox.com
    • {BLOCKED}il.in
    • {BLOCKED}rzjo.net
    • {BLOCKED}fgd.com

It does the following:

  • It executes the following dummy process:
    • rundll32.exe -{character} {random fielname}.dll
      wherein {random fielname}.dll does not exist
  • It may download additional modules from its server. However as of this writing, there was no successful connection to the server.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN DATE:

21 Apr 2016

VSAPI OPR PATTERN Date:

22 Apr 2016

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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

Scan your computer with your Trend Micro product and note files detected as TROJ_NYMAIM.YGS

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry key

[ 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.

  • HKEY_CURRENT_USER\Software\Microsoft\
  • LVFP

Step 6

Search and delete the file detected as TROJ_NYMAIM.YGS

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 7

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%\{random filename}.{random extension}
  • %All Users Profile%\{random folder name}\{random filename}.{random extension}

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_NYMAIM.YGS. 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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