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

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

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.

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 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.
• 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.

Nurech.AS 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: Downloader.PYQ.