According to the ARRL Letter, Army MARS Headquarters Operations Officer David McGinnis, K7UXO, says "we assume that all computer systems in private citizens' hands are infected with hostile software code of some sort and are not secured," regardless of antivirus and malware protection programs.
McGinnis says this is only a recommendation at this point, but notes that certain exercises will require the use of computers that are "air-gapped" from the internet.
