TBug-634 Virus

 Virus Name:  TBug-634 
 Aliases:     Andr-634 
 V Status:    New 
 Discovered:  September, 1993 
 Symptoms:    .COM & .EXE file growth; file date/time changes; 
              decrease in total system & available free memory 
 Origin:      Unknown 
 Eff Length:  634  Bytes 
 Type Code:   PRhAK - Parasitic Resident .COM & .EXE Infector 
 Detection Method:  F-Prot, Sweep, ViruScan, IBMAV, AVTK, NAV, 
                    NAVDX, VAlert, PCScan, ChAV, 
                    Sweep/N, NShld, NProt, AVTK/N, IBMAV/N, Innoc, NAV/N, 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The TBug-634 virus was submitted in September, 1993.  Its origin or 
       point of isolation is unknown.  TBug-634 is a memory resident infector 
       of .COM and .EXE programs, including COMMAND.COM. 
       When the first TBug-634 infected program is executed, this virus will 
       install itself memory resident at the top of system memory but below 
       the 640K DOS boundary, not moving interrupt 12's return.  Total 
       system and available free memory, as indicated by the DOS CHKDSK 
       program, will have decreased by 640 bytes.  Interrupt 21 will be 
       hooked by TBug-634 in memory. 
       Once the TBug-634 virus is memory resident, it will infect .COM and 
       .EXE programs when they are executed.  Infected programs will have 
       a file length increase of 634 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.  The following text string can be 
       found near the end of all infected files: 
       TBug-634 uses a mechanism similar to that employed by the Vacsina 
       virus for infecting .EXE programs.  As a result, some anti-viral 
       programs employing scanning technologies may detect this virus as 
       a variant of the Vacsina virus. 

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