Additionally, some viruses are poorly written, and may cause a computer to stop or damage files. Many viruses make the computer's memory unstable or cause programs to run improperly. Viruses will not go away anytime soon. More than 30,000 have been identified and hundreds of new ones are created every month. With numbers like these, no one who uses computers is immune from viruses.
Viruses can infect any type of file that contains executable code.
Today, many other file types can contain executable code such as word processing and spreadsheet documents that use macros, which are simple embedded programs. Other viruses infect executable code in the boot sector of floppy disks or in system areas of hard drives. And it's possible for HTML documents to spread viruses or carry other forms of malicious code through JavaScript or other similar types of script. Since virus code must be executed, files that are recognized by the computer as pure data files are generally safe. These include graphics and sound files such as .gif, .jpg, .mp3, or .wav files as well as plain text in .txt files.