Ontario III Virus

 Virus Name:  Ontario III 
 V Status:    Rare 
 Discovered:  September, 1992 
 Symptoms:    .COM & .EXE growth; decrease in system and free memory 
 Origin:      Ontario, Canada 
 Eff Length:  2,048 Bytes 
 Type Code:   PRhAK - Parasitic Encrypted Resident .COM & .EXE Infector 
 Detection Method:  ViruScan, AVTK, F-Prot, Sweep, IBMAV, PCScan, 
                    NAV, NAVDX, VAlert, ChAV, 
                    NShld, AVTK/N, Sweep/N, IBMAV/N, Innoc, NAV/N, LProt 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The Ontario III virus was submitted in September, 1992 from 
       Ontario, Canada.  The Ontario III virus is based on the 1024 SBC or 
       Ontario II virus, and is a polymorphic memory resident stealth 
       virus which infects of .COM, .EXE, overlay and .SYS files.  It will 
       infect COMMAND.COM. 
       The first time a program infected with the Ontario III virus is 
       executed, it will install itself memory resident above the top of 
       system memory but below the 640K DOS boundary.  Total system memory 
       and free memory will be decreased by 5,120 bytes.  Interrupt 21 will 
       be hooked by the virus in memory.  At this time, the virus will 
       also infect the copy of COMMAND.COM pointed to by the COMSPEC 
       environmental variable.  COMMAND.COM will not increase in size as the 
       virus will overwrite the slack space at the end of COMMAND.COM. 
       Once the Ontario III virus is memory resident, it will infect .COM, 
       .EXE, overlay (.OVL), and .SYS programs when they are executed or 
       opened for any reason.  Infected programs will increase in size by 
       2,048 bytes, though the file length increase will not be visible if 
       the virus is memory resident.  The virus will be located at the end 
       of the file. 
       The Ontario III virus uses a very complex form of encryption with 
       no more than two bytes remaining constant in replicated samples. 
       While the following text strings occur in the viral code, they are 
       not visible in infected files due to the encryption: 
               "Your PC has a bootache! - Get some medicine!" 
               "Ontario-3 by Death Angel" 
       The Ontario III virus also contains an embedded boot sector, though 
       it is never actually written out to disk.  It employs additional 
       stealth techniques to avoid its being disassembled using the DOS 
       DEBUG program.  If it detects the use of the DOS DEBUG program, it 
       will disinfect itself from the file in memory. 
       See:   1024 SBC   Ontario 

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