The CEO of a major technology company once famously opined that, in the Internet Age, “You have zero privacy. Get over it.”

Some of us would rather not. We’d like to keep our personal information – whether it be what we share with friends on Facebook or our credit card details – under some control. We’d prefer not to let such information out into the wild, where it can be bought and sold and, often, used against us.

If you, too, are a privacy traditionalist, take heart: there are things you can do to make browsing, shopping, socialising, and other online activities less of a threat. That CEO was right in some ways: we probably can’t keep all of our private information private. But we can certainly make accessing it harder for those who’d like to make it public.

Sniffers

You have to enable SSL program by program; setting it here for Mail won’t encrypt traffic from Safari

The risk Any time you use a public network, someone else could be listening in. Miscreants nearby could be sniffing your network traffic or snooping on your visits to sites like Facebook to hijack your login.

How to protect yourself First, don’t use a public WiFi network you don’t absolutely trust. Second, think long and hard about the applications and sites you use on a public network; don’t, for example, do any online banking.

Encrypt your network traffic via SSL whenever possible. It’s fairly easy to do in email clients. It’s easy to do in Safari, too: Safari defaults to SSL on sites that support it. (Again, you’ll know SSL is in effect by the closed padlock in the browser window.) For Firefox, try the HTTPS Everywhere plug-in (free; www.eff.org/https-everywhere/), which forces SSL sessions for services that support it. In the absence of that, replacing ‘http://’ with ‘https://’ works on some sites.

You can also use a VPN (virtual private network) or internet proxy service when connecting via public networks; either will make your traffic unsnoopable. Anonymizer ($80/£48 a year; www.anonymizer.com); StrongVPN (about $5/£3 a month; strongvpn.com); and PersonalVPN ($5/£3 a month; www.witopia.net) are good ones.

ISP and network tracking

The risk Internet service providers, or whoever manages the network you’re using to connect to the internet, can see all of your traffic. A number of ISPs now track their customers’ browsing and sell aggregated information to market analysis firms. As with some other privacy violations, this is more creepy than dangerous.

How to protect yourself If your ISP tracks your online whereabouts, you might be able to opt out on its website. As with ad networks, opting out of ISP tracking means setting a cookie in your browser telling the ISP to ignore your traffic. If you clear that cookie, the ISP will resume tracking. However, you can’t always fully opt out of the monitoring.

If you’re worried about your ISP or network provider sniffing your traffic, the only way to protect yourself is to encrypt the traffic (by using the same techniques described above for preventing snooping), or you could use an anonymisation service such as Tor (free; www.torproject.org). Tor encrypts your connection and routes it through a number of random servers on the internet. Your traffic is still visible at the exit node, but it can’t be tracked back to you on your local network or by your ISP. Unfortunately, Tor can significantly slow down browsing and other activities.

Stop sharing

The risk Many people forget to change their Macs’ settings when they move from their regular network to something more public. The settings that make it easy to share your files, music, and photos at home or in the office make it just as easy for strangers to stumble upon your data when you’re at a coffee shop or on a cruise ship.

How to protect yourself The first step to making sure you don’t share more than you intend is to go System Preferences, select the Sharing pane, and then turn off File Sharing. This will ensure that no one can get access to your files, or put their own files onto your Mac.

While you’re in the Sharing pane, it’s a good time to verify that no unnecessary sharing options are enabled, either. For example, if you never use Remote Login, Remote Management, or DVD, Internet, or Bluetooth Sharing, ensure that those checkboxes are unchecked. And you certainly wouldn’t want to allow password-free Screen Sharing, either.

3G or not 3G

The risk  While it’s more secure to use the 3G connection on your iPad or iPhone than to use a free, unsecured WiFi hotspot for browsing the web, there are still some risks. 3G is encrypted but, with the right equipment, somebody could intercept your information wirelessly.

How to protect yourself The iPhone and iPad include hardware-based encryption of all data. This means that unless you leave your iPhone unlocked without a password, your data is safe from all but the most skilled thieves. However, it is better to be safe than sorry, so when it comes to online banking and other transactions, it is safest to wait until you are on a secure network. Whether on WiFi or 3G, the same security rules apply. Check the authenticity of websites, don’t click on links from people you don’t know, and look out for phishing scams.