Image: Hacker examining a laptop © Gunay Mutlu, Getty Images

In his professional life, Robert Siciliano is a cybersecurity expert. But in his private life, Siciliano is a runner, and at the Boston Marathon on April 15, he was 100 yards away from crossing the finish line when the second bomb went off in a domestic terrorist attack that killed three and wounded at least 264.

Being so close to the bombing colored Siciliano's reaction to whistleblower Edward Snowden's leak of the National Security Agency's massive monitoring of telephone and Internet communications in the United States and elsewhere.

When it comes right down to it, Siciliano says he's OK knowing government spies could be tapping his phone or reading his email if it helps keep the country safe. "I'm honestly grateful for it," says Siciliano, CEO of IdentifyTheft.com. "When something like that happens, you see for yourself what's being done to prevent it from happening again in the future."

Other cybersecurity experts and privacy advocates don't share his tolerant point of view. But they do agree that if you don't want your personal information caught up in NSA monitoring or exposed by hackers or identity thieves, there are some simple things you can do to prevent it.

For starters, if you don't want the snoops snooping on you, take your communications offline. Since the odds aren't great of that happening in an age where people share the minutia of their lives on Facebook, Instagram and Twitter, the next best thing is being smart about what you share. "Try not to do stupid things," says John Kindervag, a principal analyst with Forrester Research.

In other words, don't be like former New England Patriots tight end and murder suspect Aaron Hernandez, who allegedly destroyed his home surveillance system and cell phone to hide self-incriminating evidence. "His perception was, I'll be fine because I destroyed the phone, but the tweets are coming out," Kindervag says. "If you don't want to leave any digital evidence behind, don't create any. Act like a spy. If you were James Bond, would you post this on Facebook?"

Here are other precautions that security experts recommend taking to protect yourself from spying eyes:

1. Use encryption. Popular email programs such as Microsoft Outlook and Gmail have built-in encryption. So do websites that use Hypertext Transfer Protocol Secure (HTTPS), the latest communications security protocol. You can tell whether a website has HTTPS protection by looking at the site's URL in your browser's address bar. If the URL starts with "https" instead of "http" it has an extra protection, called secure socket layer (SSL), built in. Sites with HTTPS encrypt personal data and other sensitive information that users may share on the site. Or go to the Electronic Frontier Foundation website to download extensions for Chrome and Firefox that add HTTPS protection to your browser regardless of the sites you visit.

2. Shield your IP address. Downloaded to a desktop, laptop or smartphone, software programs such as AnchorFree's Hotspot Shield or Easy-Hide-IP mask the device's IP address, rendering it undetectable by the NSA, hackers, police, Internet service providers, or anyone else.

3. Become anonymous. The Internet's version of an underground railroad is Tor, a free, volunteer-run worldwide chain of more than 3,000 Internet network relays that anyone can use to conceal their identity and Internet activity from surveillance and traffic analysis. "If you're a battered woman and hiding from a man coming after you, you could use Tor," Siciliano says.

4. Use a virtual private network. Another option for becoming the Invisible Man or Woman online is logging on through a personal virtual network. Software programs such as proXPN VPN and HMA! Pro VPN create a secure, encrypted Internet connection and masked IP address for a home computer, laptop or other device. The software can act as an extra layer of protection if you're going online over a public Wifi network at a coffee shop or airport, which might not be password protected.

5. Shop online with a virtual or single-use credit card number. Bank of America's ShopSafe and Citibank's Virtual Account Numbers programs shield customers' account information by generating a virtual credit card or single-use credit card number for online purchases. The virtual cards may be good for a single purchase or pre-set period of time.

6. Keep anti-virus updated. You may hate what it does to your PC, but if you don't have anti-virus, anti-spyware and anti-phishing software on the devices you use to connect to the Internet, and you do get hacked, you'll hate it even more.

When it comes to security, the best defense is a good offense. Siciliano says he knows his data's been hacked. "You can't worry about it," he says. What you can do is routinely monitor your bank statements, credit card bills and other accounts so if hackers or identity thieves have used your information, you can spot it and take steps to correct it. Credit card companies also monitor customer accounts for potentially fraudulent activity. But "it's your job ultimately to pay attention to your accounts," he says.

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