Ever get the feeling that someone's eyeballing you? You're probably right.
These days, between the news that the National Security Agency has been eavesdropping without warrants and that the Justice Department wants to know what searches have been conducted on Google and elsewhere, it's no wonder you feel under watch.
The real surprise, though, may be how so much of what you do on an everyday basis already gets screened, monitored, tracked, scanned and observed - often without your ever knowing it.
From spyware on your computer to police cameras on your street to GPS devices on your cell phone, how much of your private life is really private any more?
"It's all part of the general evaporation of privacy," said Peter Wayner, a Baltimore-based computer programmer who has written several books about online protocol and safety.
The Justice Department has obtained records of millions of anonymous, random searches made on Microsoft, Yahoo and America Online as it attempts to revive a child pornography law struck down by the U.S. Supreme Court. But Google, the world's most popular search engine, refused to comply, and the Justice Department has gone to court to force the company to turn over the data.
"I think the Justice Department isn't looking for personal information. They seem to want to do some research," Wayner said. "But the future may be different."
The issue has sparked privacy debates around the country - and opened the eyes of those who didn't know such records were being kept in the first place. In fact, most people leave a digital trail of personal information behind as they go about their daily life, using an ATM or a grocery savings club card or logging on to their e-mail accounts.
While most of this personal information cannot be released without a subpoena, you might be surprised at how easy it is to track where you've been and what you've done on a typical day. Consider this scenario:
Wake up, shower and dress, then before you go to work, log onto the Internet to check e-mails or a Web site.
No matter how you log onto the Web, all of your Internet activity can be traced because of your computer's Internet Protocol (IP) address, a random number that enables computers on a network to communicate.
"The IP address is like the phone number of a computer," said Wayner. "The companies usually keep the user's physical address bound to each IP address."
IP address information travels along the network of your Internet Service Provider (ISP), which acts as a conduit between your computer and the Web. Information stored by ISPs can be kept indefinitely.
"If you use a search engine for information about a bomb, your local computer has a record [of your search]," said Tim Finin, a computer science professor at the University of Maryland, Baltimore County. "Your ISP knows you're the guy who is at the address of that computer," he added, "and that you accessed the file."
Head for work, taking Interstate 95 and going through an E-Z Pass toll lane.
E-Z Pass knows you were there: Its transactions are like credit card purchases. The transponder that was placed on your windshield is read by a sensor as you pass through. Then the sensor calls up your account then verifies that it's in good standing.
"If for some reason it's not read correctly," said Teri Moss, spokeswoman for the Maryland Transportation Authority, "or if you go through an E-Z Pass lane [without a pass], a video image is taken of your license plate."
E-Z Pass would then contact the MTA, which would send you a letter requesting payment.
Just prior to approaching your office, your cell phone rings.
Some cell phones have Global Positioning System chips, enabling you to be tracked if, for example, you call 911 during an emergency.
Yet GPS devices can also alert your mobile carrier of your whereabouts throughout the day.
"If you have your phone turned on, your location is known to the phone company," said Finin. "Your cell phone is constantly communicating with the closest cell tower. Even when you're not using it, it's constantly pinging the nearest tower to say, 'I'm here. This is my number.'"
Arrive at work, swipe an access card to open the locked employees' entrance. Head to your cubicle.
Were your movements tracked from the moment you entered the building? Yes and no.
Andre Mendes, software engineer at Entry Master Systems, a Baltimore-based commercial security and access control company, said most access cards contain a coded, arbitrarily assigned number, but no personal information. Your employer, though, can match the random numbers to specific employees.
But are there surveillance cameras, perhaps inside the dark glass half bubbles you see on some ceilings, once you're inside? Department stores, government buildings, libraries and hospitals are some of the facilities that use such devices.
Officials at Diebold, an Ohio-based systems company, say some images can be stored for three months, and top-of-the-line cameras can zoom in on the minutest objects.
Said Vince Lupe, Diebold director of product management: "If you look at CSI, they zoom in on this guy's face and say, 'Let's see the mole on his left cheek.'"
Lunchtime: Order a salad with light dressing, in line with the diet your wife wants you on. The waiter brings a dessert tray with your favorite indulgence - Key lime pie. You say you shouldn't, then tell him you'll take a slice - no, two. Charge the meal to your credit card. You look around to see that no one's watching.
Yet someone is watching. Among the folks who know about your purchase: the restaurant, your credit card company, the bank that handles the restaurant's credit card account and the bank that issued your card.
Your secret is probably safe, though - unless your wife finds a good, old-fashioned paper copy of the itemized receipt in your coat pocket.
Driving back to the office takes you along city streets with several cameras attached to light posts. Stop for gas at your usual station.
It's possible that Kristen Mahoney, Baltimore City Police Department chief of technical services, is watching from monitors at headquarters, as she did recently when a rumor that some downtown gas stations were closing early prompted a mad dash to the pumps.
Mahoney dispatched nearby officers to the overcrowded stations before tempers flared.
In fact, on many of the city's busiest streets, police are watching: They've set up more than 220 surveillance cameras, mainly in crime hot spots and along downtown infrastructures.
Pod cameras with flashing blue lights that are placed in areas known for violence and drug dealing. They're watched by nearby law enforcement officers in their cars, via small, monitoring devices called footballs.
City Watch cameras that monitor light rail, trauma centers and downtown universities. Funded by a $2 million homeland security grant, they pan, tilt, zoom and record high-quality digital images.
Downtown Partnership cameras, which the non-profit organization has set up near businesses.
Port of Baltimore cameras, for port security.
Smile if you find yourself on Pratt Street at the Inner Harbor: It's monitored, Mahoney said, by the last three kinds of cameras.
After leaving work, run some errands on the way home. At the department store, pick up a new dress for your wife, who is four months pregnant and starting not to fit into her old clothes, and charge it to your store credit card. Stop at the grocery store for something to make for dinner, using your frequent shopper card for discounted prices. On your way out, hit the ATM for some cash.
In the coming days, you might receive a $50 gift certificate toward baby furniture from the department store, and coupons from the grocery store.
"If you go into a department store and buy a maternity dress, a red light goes on in the store," said Raymond Burke, a professor at Indiana University's Kelley School of Business, which has worked with retailers to analyze customer loyalty. "They know you're expecting a child and you're likely to spend upward of $5,000 on products. If they're able to analyze those purchases and tie them into the life stages of a consumer, that can be a powerful tool for promotional activity."
Burke said stores also monitor which complementary items you buy (shampoo and conditioner, hot dogs and buns) for product placement in the aisles. And they keep track of how costly it is to do business with you - how often you return purchases, for example, and in what condition.
ATMs not only record the time and amount of your transaction, but take surveillance camera images. If there happens to be a crime in the vicinity around the time you were making a withdrawal, don't be surprised if the police contact you to ask if you saw anything unusual.
Your day ends. Fall asleep with little worry about how you've been "followed" throughout the day.
Surveys have shown that most people aren't losing sleep over this issue: They don't mind forfeiting some privacy it they can see the benefits, Burke says.
Fears of terrorism and crime, for example, can make citizens accept some forms of surveillance in exchange for feeling more secure. Getting discounts, speeding through an E-Z Pass lane rather than waiting in line at the cash-only toll booth and quickly finding what you need on Google are benefits that many would be loathe to give up.
While the Justice Department controversy has raised eyebrows and prompted some search engine users to worry where their queries will end up, some experts predict people won't change their habits.
"You hear people talk about it," said UMBC's Finan, "and when push comes to shove, convenience trumps any fear about privacy."