W95.cih

The CIH virus , also known as Chernobyl , was first discovered in June 1998 in Taiwan. According to the Taipei authorities, the CIH virus was written by Chen Ing-hau, and the name of the virus derived from his initials.

CIH is a very destructive virus with a payload that destroys data. On April 26, 1999, the payload triggered for the first time, and caused many computer users to lose their data. In Korea, it was estimated as many as one million computers were affected, resulting in more then $250 million in damages.

In April 2000, although the virus is rather old, Symantec still believes the virus is in the wild and may cause damage to computer users who are using outdated virus definitions or who are not using antivirus software.

Also Known As:  Chernobyl, PE_CIH, Win95.CIH, Win32.CIH, W95/CIH.1003, CIH.Spacefiller
Type:  Virus
Infection Length:  Up to 1KB

Wild:   

• Number of infections: More than 1000
  
  
• Number of sites: More than 10
  
  
• Geographical distribution: Medium
  
  
• Threat containment: Easy
  
  
• Removal: Moderate

Damage:

• Payload Trigger:  W95.CIH V1.2 and V1.3 (April 26), W95.CIH V1.4 (26th of any month)
  
  
• Payload:  Destroys data and possible damage to CMOS

Technical details

CIH is a virus that infects 32-bit Windows 95/98/NT executable files, but can function only under Windows 95/98 and ME. It does not function under Windows NT or Windows 2000. When an infected program is run under Windows 95/98/ME, the virus becomes resident in memory. Therefore, to remove the virus you must do one of the following:

• (Recommended) Use the Symantec Security Response CIH Removal Tool , which removes the virus from memory and avoids the need to reboot from a clean system disk.
  
  
• Reboot the computer from a Rescue Disk.
  
  
• Reboot the computer from the NAV 2001/2002 CD (if your computer allows this option.)

If this is not done, the virus will infect every file that is scanned with Norton AntiVirus or with any antivirus program.

Although Windows NT system files can be infected, the virus cannot become resident or infect files on a computer running Windows NT or Windows 2000. The virus does not function under DOS, Windows 3.1, or on Macintosh computers. Once the virus is resident, CIH virus infects other files when they are accessed.

Files infected by CIH may have the same size as the original files because of CIH's unique mode of infection. The virus searches for empty, unused spaces in the file. Next it breaks itself up into smaller pieces and inserts its code into these unused spaces. When NAV repairs a file infected by CIH, it looks for these small viral pieces and removes them from the file.

There are three known variants as of April 1999 that are all very similar. CIH Version 1.2 and Version 1.3 has a payload that will trigger on April 26, commemorating Chernobyl, the Soviet nuclear disaster that occurred on April 26, 1986. CIH Version 1.4 has a payload that will trigger on the 26th of any month. The payloads for all the versions of CIH are the same.

The first payload overwrites the hard disk with random data, starting at the beginning of the disk (sector 0) using an infinite loop. The overwriting of the sectors does not stop until the system has crashed. As a result, the computer will not boot from the hard disk or floppy disk. Also the data that has been overwritten on the hard disk will be very difficult or impossible to recover. You must restore the data from backups.

The second payload tries to cause permanent damage to the computer. This payload attacks the Flash BIOS (a part of your computer that initializes and manages the relationships and data flow between the system devices, including the hard drive, serial and parallel ports, and the keyboard) and tries to corrupt the data stored there. As a result, nothing may be displayed when you start the computer. To fix this requires the services of a computer technician.

Removal instructions

There are two ways to remove this virus:

• (Recommended). Run the the CIH removal tool, and then scan with Norton AntiVirus.
  
  
• Reboot from a Rescue Disk or from a bootable CD-ROM drive using the Norton AntiVirus 2001/2002 CD.

Recommended removal procedure

The easiest way to remove this virus is to run the CIH removal tool and then scan with NAV. The CIH removal tool safely detects and removes all known strains (as of August 3, 1998) of the W95.CIH (Chernobyl) virus from memory in Windows 95 and Windows 98. If you run this tool before the virus infects your system, the tool will inoculate the computer's memory to prevent the W95.CIH virus from infecting your system until the next system restart.

CAUTION:

If the computer is infected with the W95.CIH virus, run the CIH removal tool before you try to update your antivirus definitions or scan your system. If you try to scan an infected system with an antivirus product without first running this tool, you run the risk of spreading the infection. Once you have used this tool, you can safely scan the computer.
The CIH removal tool will not detect or remove the W95.CIH virus from files. It disables the virus in memory so that Norton AntiVirus can remove the infection without inadvertently spreading the virus.

You can run the CIH removal tool from either the DOS command line or from a login script, which enables a network administrator to automate the disinfection process. Follow these steps:

• Download and run the CIH removal tool according to the instructions on the download page. Do not restart the computer until you are instructed to do so.
  
  
• Run LiveUpdate to make sure that you have the most recent virus definitions.
  
  
• Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  
  
• Run a full system scan.
  
  
• If any files are detected as infected by W95.CIH, click Repair.
  [/list=1]
  
  Alternate removal procedure
  
  This will remove the virus without the use of the tool:[list]
  
• Do one of the following:
  If your computer can boot from the CD-ROM drive and you are using Norton AntiVirus 2001 or later:[list=1]
  
  
• Place your Norton AntiVirus CD into the CD-ROM drive and restart the computer.
  
  
• When the menu appears, proceed to scan and repair viruses.
  
  
• When the scan has finished, remove the CD from the CD-ROM drive and restart the computer.
  
  
• Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  
  
• Run a full system scan.
  
  
• If any files are detected as infected by W95.CIH , click Repair.[/list=1]
  
  
• If your computer cannot boot from the CD-ROM drive or if you are using Norton AntiVirus 2000 or earlier:[list=1]
  
  
• Install Norton AntiVirus on an uninfected computer.
  
  
• Run LiveUpdate, and then run a full system scan.
  
  
• On the NAV toolbar, click Rescue.
  
  
• Follow the prompts to create a Basic Rescue set.
  
  
• Take the completed Basic Rescue set to the infected computer, and insert the "Basic Rescue Boot Disk" into the floppy disk drive. Restart the computer.
  
  
• When the Rescue Disk window appears, use the arrow keys on the keyboard to select Norton AntiVirus.
  
  
• On the command line at the bottom of the window, edit the line to read as follows:
  
  navdx /a /b+ /m+ /repair /cfg: a /log:c:nvreplog.txt
  
  and then press Enter.
  
  
  
• After the scan has finished, repeat steps 6 through 8 again, this time editing the command line to read as follows:
  
  navdx /a /b+ /m+ /delete /cfg: a /log:c:nvdellog.txt
  
  and then press Enter.
  
  
  
• When the scan has finished, the removal process is complete. Remove all disks from the disk drives, and restart the computer.
  
  
• Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  
  
• Run a full system scan.
  
  
• If any files are detected as infected by W95.CIH , click Repair.
  [/list=1]

Ps:Nu puneti spatiu intre cfg: si a!

W95.CIH.1049  is a slight variant of W95.CIH . The difference is that W95.CIH.1049 executes its payload every August 2nd.

• Also Known As:  Bloodhound.W32.EP
  
  
• Type:  Virus
  
  
• Infection Length:  1049 bytes
  
  
• Systems Affected:  Windows 95, Windows 98, Windows Me
  
  
• Systems Not Affected:  Windows NT, Windows 2000, Windows XP

Wild:   

• Number of infections:  0 - 49
  
  
• Number of sites:  0 - 2
  
  
• Geographical distribution:  Low
  
  
• Threat containment:  Easy
  
  
• Removal:  Moderate

Damage:  

Payload Trigger:  August 2nd
Payload:  Destroys data and possible damage to CMOS

Technical details

CIH is a virus that infects 32-bit Windows 95/98/NT executable files, but it can function only under Windows 95/98/Me. It does not function under Windows NT/2000/XP. When an infected program is run under Windows 95/98/Me, the virus becomes resident in memory.

Although Windows NT system files can be infected, the virus cannot become resident or infect files on a computer running Windows NT/2000/XP. The virus does not function under DOS, Windows 3.1, or on Macintosh computers. Once the virus is resident, CIH virus infects other files when they are accessed.

Files infected by CIH may have the same size as the original files because of CIH's unique mode of infection. The virus searches for empty, unused spaces in the file. Next it breaks itself up into smaller pieces and inserts its code into these unused spaces. When Norton AntiVirus repairs a file that is infected by CIH, it looks for these small viral pieces and removes them from the file.

Payload
The payload for W95.CIH.1049 executes on August 2nd.

The first payload overwrites the hard disk with random data, starting at the beginning of the disk (sector 0). The overwriting of the sectors does not stop until the system has crashed. As a result, the computer will not boot from the hard disk or a floppy disk. Also, the data that has been overwritten on the hard disk will be very difficult or impossible to recover. You must restore the data from backups.

The second payload tries to cause permanent damage to the computer. This payload attacks the Flash BIOS (a part of your computer that initializes and manages the relationships and data flow between the system devices, including the hard drive, serial and parallel ports, and the keyboard) and tries to corrupt the data that is stored there. As a result, nothing may be displayed when you start the computer. To fix this requires the services of a computer technician.