Yog Virus

 Virus Name:  Yog 
 Aliases:     Yog.794 
 V Status:    New 
 Discovered:  February, 1995 
 Symptoms:    .COM file growth; file date/time changes; 
              decrease in available free memory 
 Origin:      Unknown 
 Eff Length:  794 Bytes 
 Type Code:   PRhCK - Parasitic Resident .COM Infector 
 Detection Method:  F-Prot, ViruScan, IBMAV, AVTK, Sweep, NAV, NAVDX, 
                    PCScan, ChAV, 
                    NShld, Innoc, IBMAV/N, AVTK/N, Sweep/N, NAV/N 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The Yog virus was received in February, 1995.  Its origin or point 
       of isolation is unknown.  Yog is a memory resident infector of .COM 
       files, including COMMAND.COM. 
       When the first Yog 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 
       available memory, as indicated by the DOS CHKDSK program from DOS 5.0, 
       will have decreased by approximately 1,104 bytes.  Interrupt 21 will 
       be hooked by the virus in memory. 
       Once the Yog virus is memory resident, it will infect all of the 
       .COM files in the current directory when any uninfected .COM file 
       is executed.  Programs infected with the Yog virus will have a file 
       length increase of 794 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 strings are 
       encrypted within the viral code: 
               "*.COM *.EXE" 
               "Ha! Jsem virus Yog-Sothoth a mam te rad.Kdyz budes 
                hodnej, nezaenu ti hned formatovat hardisk.Ale treba 
                az za chvili. Ha, ha, ha...!" 
       It is unknown what the Yog virus does besides replicate. 

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