Practical Technology

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Internet Explorer Is Too Dangerous to Keep Using


OK, I confess it: I’ve used Internet Explorer a lot. After being a die-hard Netscape user, I finally got fed up with the sheer bulk of that browser and started using Internet Explorer on my Windows machines.

As time went on and open-source Mozilla matured, I started using Mozilla as my main Linux Web browser and as my secondary Windows browser. This past Friday, though, I started installing Firefox, the browser-only side of Mozilla, on every one of my production Windows machines.

Why? Because Internet Explorer, like Outlook, has finally become, to my mind, a permanent security hole that masquerades as a useful application.

Strong words? Have you really thought about this latest exploit? It could hit every Internet Explorer (IE) browser that merely visited any page served by an infected Microsoft IIS (Internet Information Server).

No anti-virus program would stop it, no firewall would slow it down and no shipping IE security patch would even notice it. Visit the page, get the infection. It was that simple.

Oh, but the few thousand people running Release Candidate 2 of Windows XP Service Pack 2 were not vulnerable to the client-side attack. And if you were one of the very few people who had all of the current critical patches installed and were running IE with its security settings at “high,” you’d be OK. That leaves, oh, say, 95 percent of all IE users wide open to this attack. I feel so much better now.

And just how bad was this attack? Boys and girls, let me tell you, this was the worst security violation I have ever seen. But dont take my word for it.

Johannes Ullrich, a handler at the Internet Storm Center at The SANS Institute in Bethesda, Md., wrote, “A large number of Web sites, some of them quite popular, were compromised earlier this week to distribute malicious code.

“The attacker uploaded a small file with JavaScript to infected Web sites and altered the Web server configuration to append the script to all files served by the Web server (IIS). The Storm Center and others are still investigating the method used to compromise the servers. Several server administrators reported that they were fully patched.”

What sites were spreading the infections? We still dont know. Neither the security companies nor the businesses running the infected sites are talking. Since theyre not being any help, I can only suggest that you update your anti-viral software and run it—now.

The only other thing I can say is that sites running IIS 5, which hadnt been patched up to Aprils MS04-011, were the ones targeted by this exploit. But, Im sorry to say, its still not clear that even sites that had been patched with MS04-011 were safe. There are reports that even patched IIS servers were infected.

What happened next was that after simply visiting what looked like a perfectly ordinary page, the JavaScript hidden with the page would direct your browser to quietly download and install one of several different programs from a Russian Web site. “These Trojan horse programs include keystroke loggers, proxy servers and other back doors providing full access to the infected system,” Ullrich said.

Many of the people talking about the exploit have discussed how your computers might be used by these back-door programs to launch a DDoS (distributed denial of service) attack. Yeah, thats bad news, but thats not the real problem.

In the few days that the sites provided the Trojan horses, hundreds of thousands or millions of users could have had their credit-card, stock-brokerage and bank-account numbers and passwords stolen.

Let me repeat myself: Millions of you may have every bit of your browser-driven online financial security information stolen.

Maybe this was just another massive Internet security prank. Maybe all that will happen is a DDoS attack. Well, you can hope thats all there is to it and continue to use IE. But as for me, Im done with it.

Yes, by Friday, most of the major anti-viral programs could stop this particular attack. But what about the next one?

According to the U.S. CERT (Computer Emergency Response Team), “Microsoft Internet Explorer does not adequately validate the security context of a frame that has been redirected by a Web server. An attacker could exploit this vulnerability to evaluate script in different security domains. By causing script to be evaluated in the Local Machine Zone, the attacker could execute arbitrary code with the privileges of the user running IE.”

There is, at this time, no shipping patch to stop this. Wonderful.

If you must run IE, and unfortunately, I do for at least one remote application I use every day, you can disable all active scripting and ActiveX on all IE zones. Between CERTs frequently asked questions about malicious Web scripts redirected by Web sites and Microsofts Knowledge Base article on how to strengthen the security settings for the Local Machine zone in Internet Explorer, you should be safe from most variations of this kind of attack.

Frankly, though, I think CERTs other suggestion is an even better one: Use a different Web browser.

Open-source browsers, such as Mozilla Firefox, are simply more secure than IE. Yes, I know all of the tired, old arguments about how if open-source programs were as popular as Microsofts products; theyd be just as vulnerable. You know what? I dont have time today to deal with the fundamentally inane idea that security by obscurity is somehow the best way to secure software.

The bottom line is that for all practical purposes for today, open-source browsers are inherently more secure than Internet Explorer, and I still have half a dozen more workstations to switch over to Firefox. Go ahead, stick with Internet Explorer for everyday use. Its your funeral.

A version of this story was first published in eWEEK.

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