Threat Explorer

The Threat Explorer is a comprehensive resource consumers can turn to for daily, accurate, up-to-date information on the latest threats, risks and vulnerabilities.



09 August 1995
13 February 2007
Also Known As:
Havoc, Wedding

Neuroquila is an infectious boot sector virus. Once a computer is infected, you can see the disk drives only when the virus is in memory. If you boot the computer from a floppy disk that does not have a virus, the drives are not accessible.

Approximately three months after infection, the virus displays the following text:

by Neurobasher Germany '93/Germany -GRIPPED-BY-FEAR-UNTIL-DEATH-US-DO-PART-

The Neuroquila virus targets the antivirus programs, ThunderByte and Central Point Anti-Virus, to attempt to prevent them from detecting the virus.

For Windows XP users only
Neuroquila is an older, boot sector virus. Norton AntiVirus has provided protection against it since 1995. There have been reports of this virus being detected on new Windows XP computers from one or more manufacturers. Although it is likely that this detection is a false positive , we have not been able to reproduce this.

In many but not all cases, this has been reported in the \Prefetch folder.

If you detect Neuroquila on a computer running Windows XP, you can delete the contents of the C:\Windows\Prefetch folder. Follow these additional steps:

NOTE: This will not harm your system. The Prefetch folder is simply a record of recently accessed files that allows frequently used files to load slightly faster. On most modern computers, this is not even noticeable. In any case, Windows will rebuild the contents of this folder.
  1. Restart the computer in Safe mode. For instructions on how to do this, read the document, "How to start Windows XP in Safe Mode."
  2. Click Start, and then click My Computer.
  3. In the right pane, double-click Local Disk (C:).
  4. In the right pane, double-click Windows.

    NOTE: If the computer has been upgraded to XP, you may need to look in the Winnt folder.

  5. In the right pane, double-click Prefetch.
  6. Click Edit, and then click Select All.
  7. Press Delete, and then click Yes to confirm.
  8. Run a full system scan.
  9. Restart the computer.

Neuroquila is an extremely infectious, highly polymorphic virus. After hooking Interrupt 13 and Interrupt 21, it resides in High-Memory Areas (HMA). The polymorphic routine that is used is based on the current system date and time.

The infected host files write the virus to the Master Boot Record (MBR) and become memory-resident, hooking Interrupt 13. Neuroquila encrypts the original MBR, partition table, and its own viral code, storing them on the first physical drive on side 0, track 0, sectors 7 through 16. To read the real partition and see the drive, Neuroquila must be active in memory.

If the user boots from a virus-free floppy disk, thus avoiding the virus, the hard drive is not accessible by normal means. In addition, Neuroquila encrypts the hard drive boot sector, although it does not move it. The MBR, boot sector, and infected host files are fully stealthed when the virus is active in memory.

Host file infection size increases according to the following formula:

infection size = 4675 - ((file_size + 4) mod 32)

Therefore, the resulting increase in host size is between 4644 and 4675 bytes. Three months with some disk usage from infection, Neuroquila displays the following text:

by Neurobasher Germany '93/Germany -GRIPPED-BY-FEAR-UNTIL-DEATH-US-DO-PART-

Neuroquila specifically targets the ThunderByte antivirus package. If this virus determines that the disk-monitoring features are enabled, it attempts to disable them. Neuroquila even goes so far as to alter some of the inoculation information that ThunderByte stores. In addition, there are references to Central Point Antivirus integrity files.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus and make sure that it is configured to scan all the files. For instructions, read, "How to configure Norton AntiVirus to scan all files."
  3. Run a full system scan.
  4. If any files are detected as infected by Neuroquila, click Repair.

NOTE : If you are running Windows XP, read the Additional Information section.