Analysis by: Alvin Bacani
ALIASES:

Virus:Win32/Pintu.A (Microsoft); Win32/Injector.AQOK (ESET-NOD32)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware, Propagates via flashdrives

This file infector arrives by connecting affected removable drives to a system. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It creates folders in all physical and removable drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 507,904 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 02 Dec 2013
Payload: Drops files

Arrival Details

This file infector arrives by connecting affected removable drives to a system.

It 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 file infector drops the following copies of itself into the affected system and executes them:

  • %Application Data%\Paint.exe

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

Autostart Technique

This file infector drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\Paint.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Propagation

This file infector creates the following folders in all physical and removable drives:

  • {Drive Letter}:\Paint

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

NOTES:

This file infector searched for all *.EXE files on all drives connected to the affected system.

It renames the targeted file to:

  • v{target filename}.exe (e.g. Calc.exe to vCalc.exe)

It replaces the file attribute of the renamed file to Hidden.

The malware then use the original filename of the target file and drop a copy of itself using the original filename.

It then retrieves the icon file from the renamed target file and updates the malware with the said icon.

Once the malware is executed, the renamed file will also be executed.

  SOLUTION

Minimum Scan Engine: 9.700

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

Scan your computer with your Trend Micro product and note files detected as PE_PINTU.A

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete these files

[ 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 Startup%\Paint.lnk
  • %Application Data%\Paint.exe
  • {Drive Letter}:\Paint
  • {Drive Letter}:\autorun.inf

Step 5

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

NOTES:

Please perform the following steps in between Solution Step 4 and 5.

Search and Replace files detected as PE_PINTU.A 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.

To replace malware/grayware files:

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

1. Right-click Start then click Search....

2. In the Named input box, type the name of the file that was detected earlier.

3. In the Look In drop-down list, select My Computer then press Enter.

4. Once located, select the file then press SHIFT+DELETE to delete it.

5. Again, in the Named input box, type the name of the file that was detected earlier, add v before the name of the file.

6. Once located, select the file then press F2 to rename the file and remove the v on the file name.

7. Repeat steps 2-6 for the remaining files.

For Windows Vista and Windows 7:

1. Click Start > Computer.

2. In the Search Computer input box, type the name of the file detected earlier, and press Enter.

3. Once located, select the file then right click the mouse and select DELETE to delete it.

4. Again, in the Search Computer input box, type the name of the file that was detected earlier, add v before the name of the file.

5. Once located, select the file then right click and select Open file location.

6. Select the file, the press F2 to rename the file and remove the v on the file name.

7. Repeat steps 2-6 for the remaining files.


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