This isn't anything new, Amiga in the 90's had a CMOS happy virus that used the battery power to stay in memory. It wasn't in the clock but rewrote that area of the working bios to stay resident. I remember having to take the battery out of my A500 to get rid of it, as it survived reboots and power offs.
I heard a rumor about the Amiga clock virus when I was an Amiga dealer in the 1990s. I didn't believe it, because I knew that the clock had too little RAM to hold a virus. Your description is much more believable.