Simply booting up a Wi-Fi-enabled laptop can tell people sniffing wireless network traffic a lot about your computer and about you. Soon after a computer powers up, it starts looking for wireless networks and network services. Even if the wireless hardware is then shut-off, a snoop may already have caught interesting data. Much more information can be plucked out of the air if the computer is connected to an access point, in particular an access point without security. There are many tools that let anyone listen in on wireless network traffic. These tools can capture information such as usernames and passwords for email accounts and instant-message tools as well as data entered into unsecured Web sites. At the annual Defcon hacker gathering, a ‘wall of sheep’ always lists captured login credentials.

Errata Security has developed another network sniffer that looks for traffic using 25 protocols, including those for the popular instant-message clients as well as DHCP, SMNP, DNS and HTTP. This means the sniffer will capture requests for network addresses, network management tools, Web sites queries, Web traffic and more. “You don’t realise how much you’re making public, so I wrote a tool that tells you,” said Robert Graham, Errata Security’s chief executive. The tool will soon be released publicly on the Black Hat Web site. Anyone with a wireless card will be able to run it, Graham said. Errata Security also plans to release the source code on its Web site.