422 Overwriting Virus

 Virus Name:  422 Overwriting 
 V Status:    Rare 
 Discovery:   March, 1993 
 Symptoms:    .COM files corrupted; file date/time changes; TSR; 
              DOS DIR command output not correct; programs fail to function 
 Origin:      Unknown 
 Eff Length:  422 Bytes Overwriting 
 Type Code:   PRsC - Overwriting Resident .COM Infector 
 Detection Method:  F-Prot, Sweep, AVTK, ViruScan, IBMAV, NAV, 
                    NAVDX, VAlert, PCScan, ChAV, 
                    Sweep/N, NShld, AVTK/N, NProt, IBMAV/N, NAV/N, Innoc, 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The 422 Overwriting virus was submitted in March, 1993.  Its origin 
       or point of isolation is unknown.  422 Overwriting is a memory 
       resident overwriting virus which infects .COM programs, but not 
       When the first 422 Overwriting infected program is executed, this 
       virus will install itself memory resident as a low system memory 
       TSR of approximately 1,120 bytes.  Interrupt 21 will be hooked 
       by the virus in memory. 
       Once the 422 Overwriting virus is memory resident, it will infect 
       one .COM program each time a DOS DIR command is executed.  The 
       command output of the DOS DIR command will also be affected, usually 
       with one .COM file name being repeated multiple times. 
       Programs infected with the 422 Overwriting virus will not have any 
       file length increase as the virus will overwrite 422 bytes located 
       somewhere in the middle of the host file.  The one exception is that 
       files which were originally smaller than the virus itself will 
       become over 65K bytes in size after infection.  The file's date and 
       time in the DOS disk directory will have been updated to the current 
       system date and time when infection occurred.  No text strings are 
       visible within the viral code. 
       Programs infected with the 422 Overwriting virus will not function 
       properly when executed. 

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