981 Virus

 Virus Name:  981 
 Aliases:     Joe's Demise 
 V Status:    Rare 
 Discovery:   May, 1992 
 Symptoms:    .COM & .EXE file growth; decrease in total system and 
              available free memory 
 Origin:      Unknown 
 Eff Length:  981 - 1,932 Bytes 
 Type Code:   PRhA - Parasitic Resident COM & .EXE Infector 
 Detection Method:  ViruScan, AVTK, Sweep, F-Prot, IBMAV, NAV, 
                    NAVDX, VAlert, PCScan, ChAV, 
                    NShld, Sweep/N, LProt, Innoc, NProt, AVTK/N, IBMAV/N, 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The 981 virus was discovered in the United States in May, 1992.  Its 
       origin is unknown.  This virus is a memory resident infector of 
       .COM and .EXE files, but not COMMAND.COM. 
       When the first 981 infected program is executed, the 981 virus will 
       install itself memory resident at the top of system memory but 
       below the 640K DOS boundary.  Interrupt 12's return will not be 
       moved.  Total system and available free memory, as indicated by the 
       DOS CHKDSK program, will have decreased by 1,952 bytes.  Interrupts 
       21 and 22 will be hooked by the virus in memory. 
       Once memory resident, the 981 virus will infect .COM and .EXE 
       programs when they are executed or opened for any reason.  .COM 
       files increase in size by 981 bytes, though if the file was 
       originally smaller than 981 bytes, they will become 1,934 bytes in 
       length.  .EXE files increase in size by 1,015 to 1,025 bytes.  In 
       both cases the virus will be located at the end of the program. 
       This virus will sometimes reinfect previously infected programs, 
       adding an additional 981 bytes to the file.  The infected program's 
       date and time in the DOS disk directory listing will not be 
       One text string can be found in all 981 infected programs: 
               "This program requires MS-DOS 3.00 or later" 
       It is unknown what the 981 virus may do besides replicate. 
       Known variant(s) of 981 are: 
       Joe's Demise: Functionally similar to the original virus, this 
                     variant has 11 bytes which differ. 
                     Origin:  Unknown  June, 1992. 

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