Sophos Support has had reports of Apple Mac OS systems where web browsing stops while Sophos is installed. Currently, this is under high priority investigation do determine the cause and correct the issue.
For more information, please refer to the below article:
This is !@#$ up my life right now. Why do you have a Mac issue every other week? Sophos is absolutely the worst Mac product I've ever used. There a concept called "Do no harm" You should study and learn it well.
BTW the fix is too restart your computer, sometimes 4 times until this clears.