CIH (computer virus)

From Wikipedia, the free encyclopedia

You have new messages (last change).

CIH, also known as Chernobyl or Spacefiller, is a computer virus written by Chen Ing Hau of Taiwan. It is considered to be one of the most harmful widely circulated viruses, overwriting critical information on infected system drives, and more importantly, in some cases corrupting the system BIOS.

The name "Chernobyl Virus" was coined some time after the virus was already well-known as CIH, and refers to the complete coincidence of the payload trigger date in some variants of the virus (actually the virus writer's birthday) and the Chernobyl accident, which happened in USSR on April 26, 1986.

Contents

[edit] History

In September 1998, Yamaha shipped a firmware update to their CD-R400 Drives that were infected with the virus.

In October 1998, a demo version of the Activision game SiN that was propagated by users got infected due to contact with an infected file on a certain user's machine. That company's infection came from a group of Aptiva PCs shipped by IBM during March 1999 with the CIH virus pre-installed. The computers were shipped around a month before the CIH payload activated for the first time in the public eye on April 26, 1999. This was a catastrophic event, and an untold number of computers worldwide were affected with the first 1024 KB of their boot drives being over-written with zeroes and even having their BIOS damaged, preventing the computer from successfully completing the POST process. By April 26, 2000, much of the damage was happening in Asia, but the virus was not as widespread there. On March 2001, the Anjulie Worm was discovered. It was honar who dropped CIH v1.2 into the system as part of its payload.

Today, CIH is not as widespread as it once was, due to awareness of the threat and the fact it only affects older Windows 9x (Windows 95, 98, and Windows Me) operating systems.

The virus made another comeback in 2001 when a variant of the Loveletter Worm in a VBS file containing a dropper routine for the CIH virus was circulated around the internet, under the guise of a nude picture of Jennifer Lopez.

A modified version of the virus called CIH.1106 was discovered in December 2002, but it is not a serious threat.

CIH is considered a threat only if it infects programs used by mass-mailing computer worms, such as Klez, or if the Anjulie Worm comes into play.

[edit] Virus specifics

CIH spreads under the Portable Executable file format under Windows 95, Windows 98, and Windows ME. CIH does not spread under Windows NT, Windows 2000, or Windows XP.

CIH infects Portable Executable files by splitting the bulk of its code into small slithers inserted into the inter-section gaps commonly seen in PE files, and writing a small re-assembly routine and table of its own code segments' locations into unused space in the tail of the PE header. This earned CIH another name, "Spacefiller". The size of the virus is around 1 kilobyte, but due to its novel multiple-cavity infection method, infected files do not grow at all. It uses methods of jumping from processor ring 3 to 0 to hook system calls.

The payload, which is considered extremely dangerous, first involves the virus overwriting the first megabyte (1024KB) of the hard drive with zeroes, beginning at sector 0. This often deletes the contents of the partition table, and may cause the machine to hang.

The second payload tries to write to the Flash BIOS. Due to what may be an unintended feature of this code, BIOSes that can be successfully written to by the virus have critical boot-time code replaced with junk. This routine only works on some machines. Much emphasis has been put on machines with motherboards based on the Intel 430TX chipset, but by far the most important variable in CIH's success in writing to a machine's BIOS is the type of Flash ROM chip in the machine. Different Flash ROM chips (or chip families) have different write-enable routines specific to those chips. CIH makes no attempt to test for the Flash ROM type in its victim machines, and has only one write-enable sequence.

For the first payload any information that the virus has overwritten with zeros is lost. Luckily provided the first partition is FAT32 and over about one gigabyte all that will get overwritten is the MBR, the partition table, the boot sector of the first partition and the first copy of the FAT of the first partition. The MBR and boot sector can simply be replaced with copies of the standard versions, the partition table can be rebuilt by scanning over the entire drive and the first copy of the FAT can be restored from the second copy. This means a complete recovery with no loss of user data can be performed automatically by a tool like Fix CIH.

If the first partition is not FAT32 or is smaller than 1GB the bulk of user data on that partition will still be intact but without the root directory and FAT it will be difficult to find it especially if there is significant fragmentation.

If the second payload goes off without a hitch, the computer will not start at all. A technician is required to reprogram or replace the Flash BIOS chip, as most systems that CIH can affect predate BIOS restoration features.

[edit] CIH v1.2/CIH.1103

This variant is the most common one and activates on April 26. It contains the string: CIH v1.2 TTIT.

[edit] CIH v1.3/CIH.1010A and CIH1010.B

This variant also activates on June 26. It contains the string: CIH v1.3 TTIT.

[edit] CIH v1.4/CIH.1019

This variant acts on the 26th of any month. It is still in the wild, although it is not that common. It contains the string CIH v1.4 TATUNG.

[edit] CIH.1049

This variant activates on August 2 instead of April 26.

[edit] CIH.110664

This is a minor, fairly recent variation that appeared on December 2002.

[edit] Influence

Most computers and even servers now include dual-BIOS to protect from corruption.

[edit] See also

[edit] External links

Retrieved from "http://en.wikipedia.org../../../c/i/h/CIH_%28computer_virus%29_b7e1.html"