McAfee > Theat Center > Virus Detail Page

Overview

This is a trojan detection. Unlike viruses, trojans do not self-replicate. They are spread manually, often under the premise that they are beneficial or wanted. The most common installation methods involve system or security exploitation, and unsuspecting users manually executing unknown programs. Distribution channels include email, malicious or hacked web pages, Internet Relay Chat (IRC), peer-to-peer networks, etc.

Characteristics

On execution, Shavr copies itself to the root of the system drive and to the system folder.  An autorun.inf file is also created in the root of the system drive.  This causes a double-click on the drive letter in Windows Explorer to launch another instance of the Trojan.  A desktop.ini file is also added, but has no effect as the single item it contains is set to an invalid value ("ConfirmFileOp=10").  The varsh.txt file contains only a short message from the Trojan author.

Two registry values are added to disable usage of the Task Manager and RegEdit.  An entry in the registry Run key is also created to launch the Trojan at each system startup.  These registry elements are re-created approximately every 30 seconds while the Trojan is running.

When the local system time is between 14:00 and 15:00, Shavr also executes a forced system shutdown with a 30 second delay.

Files Added

• %SystemDir%\varsh.txt (1 KB)
• %SystemDir%\varsh.exe (44 KB) (MD5: B09A8733984335E34510BE9A826E4360)
• %SystemDir%\autorun.inf (1 KB)
• c:\varsh.exe (44 KB) (MD5: B09A8733984335E34510BE9A826E4360)
• c:\desktop.ini (1 KB)
• c:\autorun.inf (1 KB)

Registry

The following registry keys are created:

• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  "Win32dll"="C:\Windows\System32\varsh.exe"
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\system
  "DisableTaskmgr"="1"
  "DisableRegistryTools"="1"

Symptoms

• Forced shutdown occurs between 14:00 and 15:00 local system time
• Unable to launch Task Manager or Registry Editor
• Presence of the files and registry elements previous mentioned

Method of Infection

N/A. Trojans are not viruses, and as such do not themselves contain any method to replicate. However they may be downloaded by other viruses and/or Trojans to be installed on the user's system.

Many of these additionally are mass spammed by the author to entice people into double-clicking on them.

Alternatively they may be installed by visiting a malicious web page (either by clicking on a link, or by the website hosting a scripted exploit which installs the Downloader onto the user's system with no user interaction.

Removal

All Users:
Use current engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

Additional Windows ME/XP removal considerations

Variants

Variants

N/A

All Information

Overview -

This is a trojan detection. Unlike viruses, trojans do not self-replicate. They are spread manually, often under the premise that they are beneficial or wanted. The most common installation methods involve system or security exploitation, and unsuspecting users manually executing unknown programs. Distribution channels include email, malicious or hacked web pages, Internet Relay Chat (IRC), peer-to-peer networks, etc.

Characteristics

Characteristics -

On execution, Shavr copies itself to the root of the system drive and to the system folder.  An autorun.inf file is also created in the root of the system drive.  This causes a double-click on the drive letter in Windows Explorer to launch another instance of the Trojan.  A desktop.ini file is also added, but has no effect as the single item it contains is set to an invalid value ("ConfirmFileOp=10").  The varsh.txt file contains only a short message from the Trojan author.

Two registry values are added to disable usage of the Task Manager and RegEdit.  An entry in the registry Run key is also created to launch the Trojan at each system startup.  These registry elements are re-created approximately every 30 seconds while the Trojan is running.

When the local system time is between 14:00 and 15:00, Shavr also executes a forced system shutdown with a 30 second delay.

Files Added

• %SystemDir%\varsh.txt (1 KB)
• %SystemDir%\varsh.exe (44 KB) (MD5: B09A8733984335E34510BE9A826E4360)
• %SystemDir%\autorun.inf (1 KB)
• c:\varsh.exe (44 KB) (MD5: B09A8733984335E34510BE9A826E4360)
• c:\desktop.ini (1 KB)
• c:\autorun.inf (1 KB)

Registry

The following registry keys are created:

• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  "Win32dll"="C:\Windows\System32\varsh.exe"
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\system
  "DisableTaskmgr"="1"
  "DisableRegistryTools"="1"

Symptoms

Symptoms -

• Forced shutdown occurs between 14:00 and 15:00 local system time
• Unable to launch Task Manager or Registry Editor
• Presence of the files and registry elements previous mentioned

Method of Infection

Method of Infection -

N/A. Trojans are not viruses, and as such do not themselves contain any method to replicate. However they may be downloaded by other viruses and/or Trojans to be installed on the user's system.

Many of these additionally are mass spammed by the author to entice people into double-clicking on them.

Alternatively they may be installed by visiting a malicious web page (either by clicking on a link, or by the website hosting a scripted exploit which installs the Downloader onto the user's system with no user interaction.

Removal -

Removal -

All Users:
Use current engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

Additional Windows ME/XP removal considerations

Variants

Variants -

N/A