1963 Virus

 Virus Name:  1963 
 Aliases:     V1963, 1963 OverWrite 
 V Status:    Rare 
 Discovery:   May, 1991 
 Symptoms:    .COM & .EXE file changes; decrease in available memory; 
              file allocation errors 
 Origin:      Unknown 
 Eff Length:  1,963 Bytes 
 Type Code:   PRsAK - Parasitic Resident .COM & .EXE Infector 
 Detection Method:  ViruScan, F-Prot, Sweep, AVTK, NAV, 
                    IBMAV, NAVDX, VAlert, PCScan, ChAV, 
                    LProt, Sweep/N, NShld, Innoc, NProt, AVTK/N, 
                    NAV/N, IBMAV/N, LProt 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The 1963 virus was received in May, 1991.  Its origin or original 
       point of discovery is unknown.  1963 is a memory resident infector 
       of .COM and .EXE files, including COMMAND.COM.  This virus is a 
       stealth virus, it hides its file length increase on infected files 
       regardless of whether the virus is memory resident.  It is related 
       to the Dark Avenger family of viruses. 
       The first time a program infected with the 1963 virus is executed, 
       the virus will install itself memory resident as a low system memory 
       TSR of 5,136 bytes.  Interrupt 21 will be hooked by the virus.  This 
       virus will mark its TSR as "available", though the memory is in fact 
       After 1963 is memory resident, it will infect .COM and .EXE programs 
       over 1,963 bytes in length when they are opened or executed.  The 
       virus infects the programs by writing the original first 1,963 bytes 
       of the program after the program's end of file mark, and then copying 
       itself into the first 1,963 bytes of the file.  (.EXE programs will 
       have the first 2,475 bytes of the program altered, the difference is 
       due to the .EXE header.)  Infected programs do not change in length 
       in the DOS disk directory. 
       Execution of the DOS CHKDSK on infected systems will result in file 
       allocation errors being detected.  These errors will occur on each 
       infected program regardless whether the virus is memory resident. 
       1963 is capable of disinfecting programs on the fly.  As a result, 
       an anti-viral unaware of this virus will be unable to locate it on 
       infected programs when using CRC or checksumming techniques. 
       Further, execution of an anti-viral program unaware of 1963 with the 
       virus memory resident will result in all programs which are opened 
       becoming infected. 
       It is unknown what 1963 does besides replicate. 
       Known variant(s) of 1963 are: 
       1963-B: Submitted in May, 1991 from Europe.  1963-B is similar 
               is similar in behavior to 1963.  The primary difference is 
               that it will infect COMMAND.COM when the first infected 
               program is executed.  There are 48 bytes of viral code 
               which differ from the original virus. 
               Origin: Europe 
       See:   Cracker Jack   Dark Avenger 

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