I recently purchased an iMac 5k (running Yosemite 10.10.2) and installed SophosAV. After a week or two, I noticed my gigabit internet svc from AT&T had decreased from a download speed of 925mbps to 300mbps. After a long session with AT&T support, we determined it was something on the iMac (got 900+ mbps in safe mode, but 300 mbps in normal mode). After a really long session with Apple support (who, btw, are wonderful), we determined it was Sophos that was causing the problem. I uninstalled Sophos and my internet speeds reurned to gigabit levels. If speed is important to you, I would suggest Sophos is not the AV solution for you.
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