557 Virus

 Virus Name:  557 
 V Status:    Rare 
 Discovery:   July, 1992 
 Symptoms:    .EXE file growth; file date/time changes; decrease in total 
              system and available free memory 
 Origin:      Unknown 
 Eff Length:  557 - 566 Bytes 
 Type Code:   PRhE - Parasitic Resident .EXE Infector 
 Detection Method:  ViruScan, NAV, Sweep, AVTK, F-Prot, IBMAV, 
                    NAVDX, VAlert, PCScan, ChAV, 
                    NShld, Sweep/N, AVTK/N, NProt, NAV/N, IBMAV/N, Innoc, 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The 557 virus was received in July, 1992.  Its origin or point of 
       isolation is unknown.  This virus is a memory resident infector of 
       .EXE programs. 
       When the first 557 infected program is executed, this virus will 
       install itself memory resident at the top of system memory but below 
       the 640K DOS boundary.  Total system and available free memory, as 
       indicated by the DOS CHKDSK program, will have decreased by 624 
       bytes.  Interrupt 21 will be hooked by the 557 virus in memory. 
       Once the 557 virus is memory resident, it will infect .EXE programs 
       when they are executed.  Infected programs will have a file length 
       increase of 557 to 566 bytes with the virus being located at the 
       end of the file.  The program's date and time in the DOS disk 
       directory listing will have been updated to the current system date 
       and time when infection occurred.  One text string occurs in all 
       infected programs: 
       The 557 virus doesn't appear to do anything but replicate. 

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