Ontario is a polymorphic, semi-stealth virus. It stays resident in memory and infectes all executed COM and EXE files. COMMAND.COM is infected by inserting the virus code to an unused part of the file.
Ontario will cause vague printer problems.
Two variants, 512 and 1024 bytes in size, are known.
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.