By Julia Korol

Lingering one night after hours to finish up some work, Tony Dreyfuss, one of the owners of Metropolis Coffee in Rogers Park, noticed that something wasn't quite right. Except for the giant bags of coffee stacked against the back wall, the place was deserted. And yet the Internet network claimed that 230 users were connected.

Next door and across the street from Metropolis Coffee are two 300-unit apartment buildings each giving at least 600 residents the opportunity to log onto the coffee shop's wireless network, according to Dreyfuss.

Since the widespread public adoption of Wi-Fi, coffee shops have been shiny beacons of hope for the laptop crowd of young professionals and sleep-deprived students as they sip some java and hammer away at their keyboards. But lately, more and more coffee shops are finding themselves tightening Internet network security to prevent nearby residents from surfing the Web on the shop owner's dime.

Metropolis Coffee used to provide free Wi-Fi when they first opened in December 2003, but eventually stepped up security and added password protection, Dreyfuss said. "Up until two months ago, the password was written on a chalkboard in the shop, but people would just come in, get the code and log on at home."

Dreyfuss's main concern is the slow speed that infects the entire network when hundreds of users are logged on at once. Metropolis Coffee uses its Internet connection to process credit card payments, which can also become a painfully slow process with so many people online.

In order to correct the problem, two months ago the shop began giving out single-use usernames and passwords with every purchase. Each one has a two-hour limit and has actually helped business because it forces people to buy more, Dreyfuss said.

Matthew Sherbach, 24, an aspiring actor who has visited the coffee shop a few times before, said the time restraint wasn't a turn-off. "I like the open atmosphere and the coffee, so I don't really mind having to get another cup every now and again," he said. "If I'm working that long, it's probably time for another cup by then anyway."

Metropolis Coffee wasn't the only one to make the decision against open Wi-Fi. Although other stores around the city take their chances without password protection, Bucktown's Caffe de Luca and Savor the Flavor in Lincoln Park both offer free Wi-Fi with purchase, and Lincoln Square's Cafeneo charges for its Internet from 11 a.m. to 8 p.m.

Lee Corrina Cano, owner of The Coffee Studio in Andersonville which opened in December, started off with a password system already in place. Their codes are good for one hour with purchase, but if it's not busy they'll give out another code for free, she said.

All sorts of people come to The Coffee Studio with computers, Cano said, from real estate agents writing up paperwork to moms surfing the web in between soccer practice and ballet recitals.

"It protects us and the users and makes sure that nobody's hogging the bandwidth," Cano said. The Coffee Studio uses a wireless Internet service provider called WEBbeams, which allows customers to pay a monthly fee that provides them unlimited Wi-Fi use in any location that uses the service.