'Insane' to run just one browser, says one expert

The creator of a popular Web server scripting language is so nervous about hackers stealing his personal information that he takes an unusual precaution: He launches a pair of browsers when he takes to the Internet. Rasmus Lerdorf, the programmer who authored PHP (Hypertext Preprocessor), an open-source language that can be embedded into HTML to produce dynamic pages, admits to practicing what he calls "hygienic" surfing, operating two browsers at a time. Running a single browser is simply "insane," claimed Lerdorf during a keynote address last week at the MySQL Conference in Santa Clara, Calif., because of "nine out of 10 Web sites having cross-site scripting holes." That includes the portal of his current employer, Yahoo Inc., where Lerdorf is an infrastructure architecture engineer. To protect himself, Lerdorf uses Apple Inc.'s Safari to surf personal sites and Mozilla Corp.'s Firefox for everything else. Lerdorf gets one thing right, agreed Alfred Huger, the senior director of Symantec Corp.'s security response group. He said that cross-site scripting vulnerabilities, usually XSS for short, are easily the most common kind of Web bug. XSS flaws let attackers inject malicious HTML and scripts -- including those written in JavaScript or PHP -- into legitimate, if vulnerable, Web sites. Often the attack is delivered via e-mail, with a link to what appears to be the real deal. In fact, the link includes the malicious code to trigger the vulnerability. Dupe users into clicking those links, and attackers can surreptitiously collect usernames and passwords as they're typed, or they can raid the passwords for other sites stored in the browser. Undercutting XSS exploits So why are two browsers better than one if the Web site, not the browser, is the threat? "First of all, [Rasmus] Lerdorf is a very smart guy," said Huger. "It would work. But only as long as you used one browser to surf to all the important sites, like your online bank and the sites you shop, and never used that browser for anything else." The idea is to separate all the surfing where personal information may be exposed from all other Web activities. "Theoretically, the places you trust are less likely to less likely to have cross-site scripting vulnerabilities, like your large, name-brand bank," said Huger. "So the browser you use to go to those sites is safer." And if a cross-site scripting exploit is launched by a questionable site viewed through the second browser, that browser won't store any critical information, such as bank account passwords, for the attacker to steal. Some people have taken that strategy even farther, said Huger, by splitting personal and other activities between two computers. "It's not a bad idea, simply because it's an extra layer of defense," added Roger Thompson, chief technology officer at Exploit Prevention Labs. The theory, the practice But an idea that is not bad in theory may not be smart in practice, both security experts said. "It's just not feasible for the average user," said Huger. "The reality is most users wouldn't know which one to run when," Thompson said. Ironically, Lerdorf's PHP is a major cause of Web site vulnerabilities. According to Danish bug tracker Secunia APS, the most up-to-date version of the scripting language has been tagged with eight flaws since its November 2006 release. Six remain unpatched. Lerdorf acknowledged last week that PHP's popularity and insecurity are parts of the XSS problem. There "is not much we can do" to tighten up PHP, he said during the keynote. Correct, said Huger. "The vast majority of cross-site scripting vulnerabilities are because of the programmer," he said. Amateur developers often try their hand at PHP, with sometimes disastrous results, Huger said. What's a user to do if the two-browser concept is so inconvenient as to be unreasonable? Use reason, said Huger. "Be very careful where you shop online, who you give credit card number to, how you get to your online bank," he recommended. "If you follow that advice, you'll be in good standing."

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