Abstract: A method is provided for detecting computer viruses that infect text-based files. In accordance with a preferred embodiment, a collection of virus signatures reflecting sequences of characters or instructions known to be found in such viruses is maintained on a computer system. A virus detection program is also maintained for the purpose of comparing the contents of computer files to the virus signatures. Upon execution of the virus detection program, whitespace within text-based files is transformed such that each sequence of whitespace characters is replaced by a single whitespace character. Virus signatures of viruses known to infect text files are similarly transformed. A transformed text-based file is then searched for at least one of said virus signatures. The user is alerted to a possible virus infection if any of the virus signatures are found in a file.