Scanning an External Drive with BD Mac

SteveC200

I've received an old computer from a friend -- an old Macbook. Before using it, I'd like to scan it for viruses. My thinking is to put it into target disk mode and run Bitdefender on it -- from my main Macbook Pro. But that makes me nervous that something might jump from the Macbook to the Macbook Pro. Is that a legitimate concern? And is there a better way to check the Macbook?

Thanks to anybody for any suggestions.

Steve