Not easy.
I have K9 web protection at home and my router is set up with the OpenDNS “Family Safety” which both work more or less fine, unless you try really hard to look for pritzus (which is why my wife can access my browsing history). Work is a different issue. They have a filter, but it’s not as strong as K9 and technically my boss can probably pull up my browsing history but he probably won’t unless there’s some sort of complaint.
I heard a speech by a mashkiach a number of years ago on this issue. I’ll try to convey the gist. I had mentioned that I once saw a group of bachurim in an airport, one of which was wearing a blindfold and being led about by the rest. I asked why we aren’t all going around like that all the time?
Rav Shlomo Wolbe ZT”L used to sit at the front of the bus not make any major effort to avert his eyes. He noticed that many men, mostly young bachurim, would sit in the back and stare at the floor the entire time. He commented “If you try to avoid the b’kiyus you’re just going to get the b’iyun.” In other words, unless you can guarantee that you will never look at a non-relative woman for your entire life (there are two or three tzadikim that can and do live such a life, but only with immense outside support) the first woman you see will have a much stronger effect on you, even if she’s 90 years old and toothless. So don’t go looking for problems, and try to avoid it when you can, but living as a hermit is a terrible idea.