A powerful new type of Internet attack works like a telephone tap, except operates between computers and Web sites they trust. Hackers at the Black Hat and DefCon security conferences have revealed a serious flaw in the way Web browsers weed out untrustworthy sites and block anybody from seeing them. If a criminal infiltrates a network, he can set up a secret eavesdropping post and capture credit card numbers, passwords and other sensitive data flowing between computers on that network and sites their browsers have deemed safe. Browser makers and the companies that sell SSL certificates are working on a fix. Microsoft Corp., whose Internet Explorer browser is the world's most popular, said it was investigating the issue. Mozilla Corp., which makes the No. 2 Firefox browser, said most of the problems being addressed were fixed in the latest version of its browser, and that the rest will be fixed in an update coming this week. VeriSign Inc., one of the biggest SSL certificate companies, maintains that its certificates aren't vulnerable. The attack falls into a class of hacks known as “man-in-the-middle,” in which a criminal plants himself between a victim's computer and a legitimate Web site and steals data as it moves back and forth. SSL certificates are a critical technology in assigning trust on the Web. The presence of an SSL certificate on a site is designated by a padlock in the address bar. But many people don't pay attention to whether a padlock is present or not. Browsers do care, though. Browsers are programmed to block sites that don't have a valid SSL certificate, or have a certificate displaying a Web address that doesn't match the address a Web surfer was trying to reach. If the sites aren't blocked, users are warned about potential danger, and have the option to click through. The problems outlined by researchers center on a quirk in the way browsers read SSL certificates. Many SSL certificate companies will allow people to attach a programming symbol called a “null character” into the Web address onto the certificates they receive. Web browsers generally ignore that symbol. All a criminal would need to do is put the name of a legitimate Web site before that character, and the browser will believe that the site it's visiting — which is under the criminal's control — is legitimate. The criminal could then forward the traffic onto the legitimate site and spy on everything the victim does on that site. This highlights a significant weakness in the very technology widely used to assure people it's safe to navigate sensitive sites. - APWhat is SSL? Short for Secure Sockets Layer, SSL certificate is a protocol developed by Netscape for transmitting private documents via the Internet. Sites buy them to encrypt traffic and assure visitors it's fine to enter confidential information. Companies that sell SSL certificates verify that someone trying to buy a certificate actually owns the site that certificate will be attached to. This is how it works. • A browser requests a secure page (usually https://). • The web server sends its public key with its certificate. • The browser checks that the certificate was issued by a trusted party (usually a trusted root CA), that the certificate is still valid and that the certificate is related to the site contacted. • The browser then uses the public key, to encrypt a random symmetric encryption key and sends it to the server with the encrypted URL required as well as other encrypted http data. • The web server decrypts the symmetric encryption key using its private key and uses the symmetric key to decrypt the URL and http data. • The web server sends back the requested html document and http data encrypted with the symmetric key. • The browser decrypts the http data and html document using the symmetric key and displays the information. __
