BKDR_MEVADE.A

This malware is associated with the reported increase in the number of Tor users. It has the capability to execute commands and download adware on to the infected system. Based on our research, Tor can be used to hide C&C servers.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

Arrival Details

This backdoor 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 backdoor drops the following copies of itself into the affected system:

• %System%\TrustedInstaller.exe
• %System%\uti.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops the following non-malicious file:

• %System%\~stg

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
Type = "20"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
Start = "02"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
ImagePath = "C:\WINDOWS\system32\TrustedInstaller.exe" /svc

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
DisplayName = "Trusted Installer"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Trusted Installer
Description = "Adds, modifies, and removes applications provided as a Windows Installer (*.msi) package. If this service is disabled, any services that explicitly depend on it will fail to start."

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\Trusted Installer

The scheduled task executes the malware at the following period:

• %Windows%\Tasks\TrustedInstaller Update.job - executes the malware daily every one hour
• %Windows%\Tasks\TrustedInstaller Update 2.job - executes the malware at system startup

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Other System Modifications

This backdoor creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path}\{malware filename}.exe = "{malware path}\{malware filename}.exe:*:Enabled:{malware filename}.exe(in)"

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\TrustedInstaller.exe = "%System%\TrustedInstaller.exe:*:Enabled:TrustedInstaller.exe(in)"

Backdoor Routine

This backdoor executes the following command(s) from a remote malicious user:

• Perform remote connection to a certain location supplied by the remote user using SSH
• Update copy of itself

It connects to the following URL(s) to send and receive commands from a remote malicious user:

• http://{BLOCKED}statistic.net\er
• http://{BLOCKED}ystatistic.com\er
• http://{BLOCKED}atistic.com\er
• http://{BLOCKED}-update.net\er
• http://{BLOCKED}ice.net\er
• http://{BLOCKED}-stat.com\er
• http://{BLOCKED}statistic.net\br
• http://{BLOCKED}ystatistic.com\br
• http://{BLOCKED}atistic.com\br
• http://{BLOCKED}-update.net\br
• http://{BLOCKED}ice.net\br
• http://{BLOCKED}-stat.com\br

NOTES:

It contains Anti Virtual Machine Execution. It checks for the presence of the following related processes

• VirtualBox
• VMWare

It also includes Anti-Sandbox, where it does not proceed with execution if found running on the following sandbox:

• Sandboxie

It requires the following parameters to be able to execute properly:

• /svc
• /w
• /i
• /r

It collects the following system information, and then sends this information to the remote user:

• UUID
• Operating System
• Installed AV products
• Installed Firewall Products