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Panda Protection

Virus Encyclopedia

Welcome to the Virus Encyclopedia of Panda Security.

Nurech.B

Threat LevelLow threatDamageHighDistributionNot widespread
Common name:Nurech.B
Technical name:Rootkit/Nurech.B
Threat level:Medium
Alias:Nurech.Z,
Type:Worm
Effects:   It spreads and affects other computers. It collects email addresses stored on the infected computer. It affects the productivity of the computer, the network to which it’s connected or other remote sites. It carries out actions that decrease the security level of the computer. It uses stealth techniques to avoid being detected by the user. It uses anti-monitoring techniques in order to prevent it being detected by antivirus companies. It spreads , via emailand also by being downloaded by other malware.
Affected platforms:

Windows 2003/XP/2000/NT/ME/98/95

First detected on:April 13, 2007
Detection updated on:April 13, 2007
StatisticsNo

Brief Description 

    

Nurech.B is a worm that spreads by copying itself, without infecting other files.

 

It captures certain information entered or saved by the user, with the corresponding threat to privacy: email addresses.

 

It affects productivity, preventing tasks from being carried out:

  • In the affected computer: causes system slowdowns.
  • In the local network: it generates a large amount of network activity and consumes bandwidth.
  • On remote sites: it mass mails junk mail (spam).

 

It reduces the security level of the computer: it terminates processes belonging to security tools, such as antivirus programs and firewalls, leaving the computer defenseless against attacks from other malware; it changes system permissions, decreasing the security level.

 

It uses stealth techniques to avoid being detected by the user:

  • It uses techniques included in its code to hide itself while it is active.
  • It injects itself in running processes.
  • It deletes the original file from which it was run once it is installed on the computer.
  • It modifies system permissions in order to hide itself.

 

It uses several methods in order to avoid detection by antivirus companies:

  • It terminates its own execution if it detects that it is being executed in a virtual machine environment, such as VMWare or VirtualPC.
  • It prevents scanning tools from running, such as Windows Registry Editor, FileMonitor, etc.
  • It terminates its own execution if it detects that a memory dump program is running, such as Procdump.
  • Its code is encrypted and it is only decrypted when it is going to run. Because of this, its code is not legible through a memory dump.
  • It terminates its own execution if it detects that a debugging program is active.

 

Nurech.B uses the following propagation or distribution methods:

  • Exploiting vulnerabilities with the intervention of the user: exploiting vulnerabilities in file formats or applications. To exploit them successfully it needs the intervention of the user: opening files, viewing malicious web pages, reading emails, etc.
  • Email: sending emails that include a copy of itself as an attachment. The computer is infected when the attachment is run.
  • It is dropped or downloaded to the computer by other malware specimens, for example: Nurech.Z.