Also known as a footbath, a sheepdip is the process of checking physical media, such as floppy disks or CD-ROMs, for viruses before they are used in a computer. Typically, a computer that sheepdips is used only for that process and nothing else and is isolated from the other computers, meaning it is not connected to the network. Most sheepdips use at least two different antivirus programs in order to increase effectiveness. The goal of sheepdipping is to block viruses from entering systems rather than waiting until they manifest on user workstations at which time they will have already done their damage. Sheepdipping is not used for files downloaded from the Internet unless the files are first transferred to a physical removable medium and run through the sheepdip before loaded onto the workstation's hard drive.
The term comes from the practice in sheep farming of dipping the sheep in chemical solutions to clean their wool of fleas and lice or to promote the healing of skin irritations.