Malicious software is the software that is loaded onto your computer to steal information, destroy information, or take over your computer system. It is the “computer software or firmware intended to perform an unauthorized process that will have an adverse impact on the confidentiality, integrity, or availability of an information system. This definition includes a virus, worm, Trojan horse, or other code-based entity that infects a host, as well as spyware and some forms of adware.”
Source: CFR 252.204–7012 Safeguarding covered defense information and cyber incident reporting.