PE_URSNIF.C

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

Arrival Details

This file infector arrives via removable drives.

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 files:

• %Application Data%\{Random Folder}\{Random Filename 1}.exe
• %System%\{Random Filename}.exe
• %User Temp%\~{Numbers}.tmp.pdf

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %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.)

It creates the following folders:

• %Application Data%\{Random Folder Name}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Value} = "%Application Data%\{Random Folder}\{Random Filename}.exe"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{Random}
Description = "{Random}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{Random}
DisplayName = "{Random}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\rdsaimon
ImagePath = "%System%\{Random Filename}.exe -s"

Propagation

This file infector drops copies of itself in the following drives:

• Removable Drives
• Network Drives

It drops copies of itself in network drives such as the following:

• {Drive Letter}:\Temp.exe

It drops the following copy(ies) of itself in all removable drives:

• {Drive Letter}:\Temp.exe

Other Details

This file infector connects to the following possibly malicious URL:

• http://{BLOCKED}.{BLOCKED}5.156.80/pki/mscorp/crl/msitwww2.crl

NOTES:

It infects .EXE and .PDF files in the said drives.