CIH virus

 Virus Information - CIH virus:

Win95.CIH (Also known as CIH, Spacefiller, Win32.CIH) is a new virus that infects 32-bit Windows 95, Windows 98 and Windows NT executables files having the .EXE extension. When an infected program is run in a Windows 95 or Windows 98 computer, it infects the computer and becomes memory resident. The infected program will not work properly on a Windows NT computer. Once the virus becomes memory resident, it infects all the 32-bit EXE files opened. So the virus spreads to all files executed and also copied. The size of the virus code is quite small and it is about 1000 bytes. The virus will not increase the size of the infected file. It uses an unique method to copy its code to the infected file. It fills up the unused space available in the 32-bit EXE file (PE format) with its code. If the virus can not find a single continuous large enough empty space to copy itself, it will slice itself up to many pieces and place them in the smaller empty slots. This virus is also known as Win95.Spacefiller for this behaviour. The virus alters the header entry point to the beginning of the virus code and builds the broken up parts to one piece of code when the EXE file is run. The virus code contains the text "CIH", so it gets this name.