A modified version of an existing virus. A variant is usually deliberately produced by the virus author or another person amending the virus code. If changes to the original are small, most anti-virus products will also detect variants. However, if the changes are large, the variant may go undetected by anti-virus software. McAfee identifies variants by a letter-based extension after the virus family name (e.g., W32/Virus. A, W32/Virus. B). When more than 26 variants of a virus are identified in a single family, a two-letter extension is used (e.g., W32/Virus. Aa, W32/Virus. Ab).