This is refering to software that can detect the presence of a virus within a computer file and warn you there is a problem.
The anti-virus software may then offer to 'quarantine' the file so it cannot be used to spread the virus.
Many packages will also try to remove the virus, but this is not always successful.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Anti-Virus Software