One of the big technology stories of 2013 has been ‘PRISM gate’ — the revelation that the National Security Agency has been secretly accessing the private data of U.S. and international citizens who use web-based services from the likes of Google (GOOG), Yahoo (YHOO), Facebook (FB) and others. Even if tech companies aren’t directly making use of your personal information, they’re still collecting and storing it, leaving it vulnerable to hackers, rogue employees and government agencies.

The NSA has also been accused of spying on the tech companies themselves and intercepting data without their consent. According to one report, the NSA collected 181 million new records in January from Google and Yahoo alone. If you own a computer, smartphone, tablet or other connected device, there’s a good chance this surveillance has ensnared some of your information.

Apple (AAPL), Microsoft (MSFT) and other tech stocks have banded together to lobby Congress to enact reforms covering how the NSA goes about collecting this data. After all, having their names embroiled in this privacy mess is not only bad PR, it also threatens to cost them money — big money — as a result of lost business.

Here’s a list of five tech stocks that may know a lot more about you than you realize: some of the biggest technology companies on the planet, plus one company you’ve probably never heard of that puts the rest to shame when it comes to personal data collection.

5 Tech Stocks Collecting Your Personal Information: AAPL

Apple may not be the first of the tech stocks that come to mind, but when you think about it, AAPL has a lot of hooks.

Every time you buy or rent iTunes content, that purchase ties back to an Apple ID that includes personal information like your credit card number, mailing address, e-mail address and phone number. The company also uses its iBeacon technology to track users in AAPL stores and its web services use cookies to retain user preferences.

Use iCloud? Documents, photos and your other data is stored on Apple servers. Then there’s the data that AAPL says is either encrypted or not saved: fingerprints from the Touch ID sensor on the iPhone 5s, Siri queries, iMessage conversation, Map searches and FaceTime video chats.

The company was on the defensive in 2011 when security researchers discovered the iPhone and iPad were tracking their owners’ every move while they were connected to cellular networks, storing locations and times in a cache file. Worse, this data was being stored in an unencrypted file. And it was named as one of the companies involved in the NSA surveillance affair, with AAPL admitting to receiving thousands of requests from law enforcement agencies for access to customer data.

5 Tech Stocks Collecting Your Personal Information: NFLX

Of course Netflix (NFLX) has access to whatever personal and financial information you supplied to sign up and pay for the streaming video service.

However, NFLX also needs to know your viewing habits if it’s going to continue to be successful. So it only makes sense that NFLX has a great deal of personal information related to how you use its service. What shows or movies you watch is a no-brainer, but it tracks much greater detail.

It knows device you use to watch with (yes, NFLX knows you got a new iPad the second you log in to watch Sons of Anarchy), the date and time you view content, when you paused or fast forwarded, what you search for, whether you come back after pausing or leaving content and your ratings for any content.

Tracking your likes, dislikes and viewing habits means NFLX can offer more accurate personal  recommendations to keep you as a customer, while your data as an aggregate helps it to decide on future programming to attract more viewers. So it’s for your own good, but it’s a little creepy.

5 Tech Stocks Collecting Your Personal Information: GOOG

As the world’s most popular search engine — and one of the hottest tech stocks — Google has access to a personal information that a lot of people would rather keep out of the spotlight.

Even if you’re not signed in to a GOOG account, searching a term then clicking on a result link may send unique identifiers (like the search term you typed, your computer IP address and location) to an advertiser. If you’re logged in, it gets worse with GOOG saving all your searches in its database.

But GOOG also has dozens of other services, and when you combine those with a Google account, the company knows an awful lot about you, from the details of every credit card in your Google Wallet to your most frequent contacts and every Gmail message you’ve ever sent or received. And all those GOOG searches … Check out this infographic for a scary look at how much Google knows about one Wall Street Journal reporter.

5 Tech Stocks Collecting Your Personal Information: FB

While people can accuse Google and other tech stocks of sneakily collecting personal info, there’s one company whose customers willingly offer up an incredible amount of the most private information imaginable!

It doesn’t take a genius to realize just how much Facebook knows about you. Although it’s all stored on FB servers — every photo, ‘Like’ and message — there’s a difference between public information and private information when it comes to whether FB and its partners make use of that information. But not everyone understands the rules fully.

Those rules also have a habit of changing over time as FB moves to monetize its customer base, and there’s always the possibility of glitches making private information suddenly very public. Even Mark Zuckerberg has had his personal photos exposed publicly — and if the FB CEO is at risk of losing his privacy, that means just about anyone could be the victim next time.

5 Tech Stocks Collecting Your Personal Information: ACXM

There’s a good chance you’ve never heard of Acxiom (ACXM). But there’s an even better chance the company has heard about you.

ACXM works with companies in many industries, including banking, insurance, retail, consumer technology, broadcasting and transportation. It collects billions of pieces of information daily and uses technology to stitch together what can be incredibly detailed (and intrusive) profiles of individuals.

ACXM can learn details such as social security numbers, address, age, credit bureau score and medical conditions. It also tracks more nuanced information like musical preferences, travel preferences and even if someone stands to potentially gain from an inheritance. And marketers can buy that information.

ACXM’s reach has become so pervasive that to defend against privacy concerns, it recently launched a consumer portal so individuals could log in to see some of the information the company had collected, verify that it is true and optionally opt out of some marketing databases — although doing so doesn’t actually delete that file Acxiom has compiled.

And lest you have doubts about just how valuable your personal information is, ACXM’s performance should enlighten you. The data broker is currently trading at more than $38, up 194% during the past two years of consistent gains for a market cap of $2.81 billion.

As of this writing, Brad Moon did not hold a position in any of the aforementioned securities.