My iMac has, since installing Yosemite, refused to stay asleep. Also, before Yosemite, Sophos would detect viruses but never finish deleting them. When the iMac would sleep (before Yosemite), it would take a long time to wake up, with the beach ball spinning for minutes. In addition, I needed to restart every few days because the spinning beach ball would come on even when typing.
I've now removed Sophos, and the iMac (late 2009) is like a new machine. Much faster; no spinning beach ball; no problem with staying asleep.
Given that since 1984, I've found perhaps two viruses that might have been a problem (the rest are .exe files which I never open), I'll take my chances without an anti-virus program.
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