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Cross-Site Scripting Worm Floods MySpace
Posted by
Zonk
on Fri Oct 14, 2005 08:25 AM
from the why-would-you-want-to-do-anything-on-myspace dept.
from the why-would-you-want-to-do-anything-on-myspace dept.
DJ_Vegas writes "One clever MySpace user looking to expand his buddy list recently figured out how to force others to become his friend, and ended up creating the first self-propagating cross-site scripting (XSS) worm. In less than 24 hours, 'Samy' had amassed over 1 million friends on the popular online community. According to BetaNews, the worm's code utilized XMLHTTPRequest - a JavaScript object used in AJAX Web applications and was spreading at a rate of 1,000 users every few seconds before MySpace shut down its site. Thankfully, the script was written for fun and didn't try to take advantage of unpatched security holes in IE to create a massive MySpace botnet."
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MySpace Worm Creator Sentenced 387 comments
Aidan Steele writes "Remember Samy? The creator of the infamous worm was unfortunate enough to be the the target in MySpace's latest litigation. As was said in the earlier story, the script was "written for fun" and caused no damage. The source and technical explanation for the "attack" was not even released until after MySpace had patched the vulnerability. Apparently this was enough to get the 20 year old (19 at the time of writing the worm) three years of probation, three months of community service, pay restitution to MySpace and is also banned from the Internet. Clearly, disclosing security vulnerabilities doesn't pay."
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XSS? (Score:5, Informative)
XMLHTTP has a same-site policy... the problem here is they let users render html & javascript in their own pages on the site. If slashdot allowed executable javascript in the comments, we'd have the same problem.
Re:XSS? (Score:5, Informative)
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Re:XSS? (Score:3, Informative)
"he split the word 'JavaScript' into two lines", and "MySpace has stripped out JavaScript and <script> tags for at least a year and a half"
IE is too forgiving (Score:5, Insightful)
In the past, I've been of mixed feelings with IE correctly rendering the "intent" of a web-designer when the web-designer has created buggy HTML - this includes such things as omitting terminating tags (e.g., <l\li>) as well as a few other things. The result of IE doing this was that some web pages look good in IE that didn't look good in other browsers - thus encouraging more people to use IE. As HTML was being used more and more by the masses, there seemed some logic to this. Of course, one of the problems with this idea is that the designers were looking at their web-pages in IE to see if their code was written correctly.
This story just goes to emphasize the importance of calling buggy HTML code what it is, and not trying to infer the intent of the HTML coder. Samy cleverly found a way to make "buggy code" that would get past MySpace's filter, but that would be rendered the way he intended by the browser with the majority market share.
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Re:IE is too forgiving (Score:5, Insightful)
pseudo-c code:
if (tagname == "style" && tagtype == "text/css") {
} else if (tagname == "style") {
}
But hopefully something less obvious that doesn't scream security flaw.
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No irony was intended (Score:5, Funny)
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Re:No irony was intended (Score:5, Funny)
Blame Heisenberg. At any given time every key is either pressed or not until you hit "submit" and find out for sure.
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Re:No irony was intended (Score:5, Funny)
Heisenberg? Wouldn't that be Schrodinger?
Heisenburg just says that you can never really be sure where the keys actually are, or your fingers for that matter.
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Re:No irony was intended (Score:5, Funny)
I have Schroedinger's wavefunction equation tattooed on my arm, and every time someone asks about it, I explain about the cat and the two-slit experiment. It would probably be more effective if I printed out pamphlets, because there isn't enough time to even explain the cat properly if a grocery-store clerk asks.
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Re:That's Irrevellant (Score:4, Insightful)
That's not the right attitude. The problem lies with web browsers that accept non-standard code.
Malicious code comes in two flavours - code that is outright malicious, and code that is completely benign in browsers that conform to the W3C specifications, but is interpreted wrongly by some browsers to generate a malicious effect.
The first type is easy to filter out, because you can go to the spec and see how things are meant to be interpreted, and from that determine what should be filtered out. The other type, though, is much harder to filter out, as you also need to be aware of all the little quirks and foibles of all browsers likely to be used to access your web application - something that isn't written down anywhere most of the time.
For example, you might have written code that strips out HTML tags. That's fine, except some versions of Netscape Navigator 4.x treat entirely different Unicode characters as if they were < and >. As a web developer, you have no way of knowing about this unless you are privy to some of the most obscure browser trivia in the world, so unless you take a default deny policy and outlaw any non-ASCII characters (goodbye international visitors), you are likely to write code that is vulnerable to this attack - for Netscape 4 users.
Now multiply that problem by all browsers in use today, and all the little quirks and deviations from spec. that they have, and you'll start to get an idea of why it's not feasible for web developers to be responsible for this problem, and why the responsibility lies at the browser developers' feet.
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Re:That's Irrevellant (Score:4, Informative)
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LiveJournal Took up the Responsibility (Score:5, Informative)
I completely agree that IE is the problem, but to say that this is something site administrators couldn't have been prepared for is untrue. To expect a self replicating javascript? No way. But to secure the filter to prevent multiline tags? Yes, cleanhtml.pl already does. It's known and out there already.
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Re:XSS? (Score:5, Funny)
Given its userbase, if Slashdot allowed this, it would have far far far worse problems. Like "if you ever read the wrong Slashdot comment with Internet Explorer, you'll leave a goatse picture on every ASP and Cold Fusion website you visit thereafter..."
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Re:XSS? (Score:5, Funny)
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Re:XSS? (Score:5, Informative)
From what I gather, you can upload CSS tags and other non-harmful tags. However, 'Samy' managed to find out that instead of writing valid CSS code inside the CSS tag, you can simply write a Script tag (so long as you split it over two lines) and upload it that way.
This in itself shouldn't be a problem; since the code is inside a CSS tag it should be parsed as invalid CSS code, and so there's no reason for MySpace to have blocked it.
This is where IE comes into it, if you are using IE, IE will parse it as a valid Javascript tag anyway, and execute the code.
This isn't really a bug in MySpace (well, technically it is now), it's more like a bug in IE which can be exploited on MySpace, or any other site which allows similar tags in which code can be 'hidden'.
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AJAX vuns (Score:3, Insightful)
Re:AJAX vuns (Score:3, Informative)
Aww... (Score:5, Funny)
Re:Aww... (Score:5, Funny)
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Re:Aww... (Score:5, Insightful)
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I find this amusing... (Score:5, Interesting)
So this guy found a way to win the popularity contest. I scoff at him too, though at the same time I must laud him for his creativity. If other
Re:I find this amusing... (Score:4, Interesting)
I've got a Myspace page, because it's the most convenient way to keep in touch with some of my old classmates. I've often thought about how few practical applications these kinds of 'social networking' sites provide, aside from general time-wasting. I've also scoffed at the number of young kids who have thousands of friends, as if it's the high school popularity contest in digital form.
Yeah, well, you're gonna expect that anywhere i guess. LiveJournal, Xanga, MySpace, BlogSpot, where-ever. I personally think MySpace does the best job of 'bringing it all together', though (blogs, message boards, friends, profiles, it's all so interconnected).
That said, MySpace is probably one of the worst-written sites of all time. Tom seems like a swell guy (i've talked to him a few times), but he and/or his team couldn't design a site if their lives depended on it. I mean that in terms of both the HTML and the 'server-side' stuff. They're constantly doing maintenance (which hardly ever seems to fix anything); they do completely random text-filtering (like you can't say '% of', the system will strip it out); the time zones are always wrong; you have to post blogs twice sometimes in order to get the auto-formatting to work; their HTML/CSS is terrible (most of their ids and classes have illegal names); the blog's design editor is retarded because the default style sheet is set to override your custom style sheet (so i'm not sure what the point is of even having the option); and so on.
Tom says he's working on a 'CSS-friendly' version of MySpace, and it seems like that's the case because suddenly there's a bunch of unused stuff if you look at the style sheet, but i have doubts that it's actually going to be much better. ... Or if it's even going to be 'CSS-friendly'.
:shrug:
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Go Samy! (Score:4, Funny)
More info... (Score:5, Informative)
Evidently LiveJournal and other sites take care to scrub out JavaScript in user-provided web pages, but the rumors are that sometimes people do figure out how to obfuscate their HTML enough to deliver the payload, despite the scrubbers.
Re:More info... (Score:5, Insightful)
- Defining "badness" instead of "goodness"
- Trying to "clean up" invalid code
The first one means that you try to list all of the ways that the input can be bad. The Universe is evil and it hates you. You can't list all the funky things that it can do to you. Instead, list the good things and carefully verify that the input is good.For a simple, but very very real-world example, don't write a rule that says "If the password contains
The second mistake is that once you've decided that input is bad, do not try to clean it up. The process of cleaning it up may itself make it invalid in the case of something like HTML. Just reject it with a good error message and let the user take care of it.
If that is absolutely impossible, preferably on the lines of "you'll be fired if you don't clean it up", then at the very least, you must continue to recursively run the cleanup code until the input converges (is unchanged by the cleanup code).
It's not that it's absolutely impossible to get it right if you don't follow these rules, it's just that it's really freakin' hard. Slashdot, for instance, does seem to manage, but it took them a few iterations and ultimately, it's a low-priority site even if it does get hacked a little. Is your program that unimportant?
It's way, way easier to define legit HTML (specific tags, no attributes usually though it's easy to let a few specific ones through, even with a handful of specific values) than it is to create a function to take any arbitrary string and make "safe" HTML out of it.
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Re:More info... (Score:4, Insightful)
No, we're not. We're talking about HTML, or things that end up as HTML. (For instance, Wiki formatting, UBB formatting, etc.) It's not English text that spread like a virus, it's code.
If you can't figure out how to write something that identifies good HTML, then you absolutely, positively should not be writing code for the web. If you think HTML is "free-form content", you're part of the problem.
The "badness" you are trying to prevent is distinguishable from the "goodness" only by the patterns that it occurs in.
No shit. You are aware that there are decades of work in computer science on the topic? And that the relevant work is all nicely packaged up as libraries that don't even require to really understand said decades of work?
All you have to do is hook up an HTML parser, and reject the content the instant you see anything bad; tags not in the approved list, attributes not in the approved list, etc. For extra bonus points to defend against a bad parser you might consider re-outputting the HTML from the parse tree via your own code that can be guaranteed to only produce safe, code-free HTML by construction, but that's generally unnecessary because for someone who actually knows what they're doing an HTML parser is not that hard, and the crappy/buggy ones generally stay very safely un-famous. (An HTML parser that gracefully handles the shitty HTML on the web today is quite a different story, but that doesn't apply here; you shouldn't be using such a thing for verification.)
If you truly find this hard, you need to either grow your skills until it isn't, stop programming for the web, or batten down the hatches and prepare for the day when something crappy like this happens to your site. The same extends to anytime user input may be interpreted as code that affects anyone else, too. I'm not the one presenting you with these choices; I'm just explaining the situation. It's just that this is how it works, in the real world. "But it's hard!" doesn't change anything.
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Back in my day (Score:5, Funny)
And the phrase for self-replicating viruses was... (Score:5, Funny)
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Re:Back in my day (Score:5, Funny)
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Awsome (Score:5, Funny)
Here's the Guys Explanation of his code (Score:5, Informative)
And here [namb.la] is his version of the story.
He comes off as a sweet practical joker. But maybe that's just b.s. that he cooked up after he realized he might have some 'splainin' to do.
Also, his site really is "namb.la" -- he's making some sort of joke at NAMBDLA's expense, which is pretty suspect, I think.
Re:Here's the Guys Explanation of his code (Score:5, Funny)
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Re:Here's the Guys Explanation of his code (Score:5, Funny)
LOL No kidding! "Here's the home page of the guy famous for writing viral web code that infects your browswer, wanna go see it?" Golly, sounds like a swell idea, what's the worst that could happen?
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With a name like MySpace... (Score:5, Funny)
... it shouldn't be surprising that someone took it literally and tried to claim it all for himself.
EricWilliam Shatner boldly goes like no man has before [ericgiguere.com]
samy is my hero (Score:5, Informative)
In the beginning (Score:3, Insightful)
Re:In the beginning (Score:3, Informative)
myspace is certainly addictive though
Interview with "Samy" (Score:3, Informative)
samy is my hero (Score:5, Informative)
Samy's info on the topic (coral) [nyud.net]
His explanation of how it works [namb.la]
Don't you hate when you forget stuff? (Score:5, Funny)
XSS basics (Score:5, Informative)
The exploit involves placing javascript code into your posting on a website, such that when other people visit the website their browsers download your comment with the embedded javascript, which is then processed. The javascript, because it is being processed on your machine as part of the rendering of the page, can be used to exploit all sorts of vulnerabilities within browsers. When you have browsers tightly coupled with operating systems, this can open up some rather scary scenarios.
In this case, the guy just used the vulnerability to make some relatively benign changes, but he could have just as easily exploited some of the many problems with IE to be more malicious.
Obligatory... (Score:3, Funny)
Unpatched security holes? (Score:3, Funny)
About (2?) years ago (Score:5, Interesting)
Mine propagated faster than this one because it didn't rely on profile views. Anytime you saw the name, whether it be in a comment, profile, or search, you would be infected. However, with the script executing 100 times per page view, myspace's servers quickly became overloaded and crashed (I didn't really expect it to work). I also essentially staged a DDoS attack against my web server which was hosting the script (it needed to be hosted in order to fit in the 'name' field).
Another note: myspace never removed the scripts that were saved before they outlawed javascript. To this day, I can read a user's inbox and sent messages when they view my profile. I also was going to write a DHTML roleplaying game that ran on myspace, but they locked that account because of the virus. It still plays music and lets you manipulate your inventory though =D
How he did it (Score:4, Informative)
http://namb.la/popular/tech.html [namb.la]
Re:Day late, dollar short. (Score:5, Insightful)
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Re:Day late, dollar short. (Score:4, Insightful)
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Re:Well, people have been saying it's a security r (Score:5, Insightful)
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Re:XMLHttpRequest (Score:4, Informative)
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Re:Quick and Dirty solution (Score:5, Interesting)
while (1) {alert("nope!");} Will DOS any browser in use today. You'll have to kill it via some OS level functionality, because alerts are modal and prevent interaction with the browser chrome. I understand that the JS spec is based on "run to completion", but is there any reason why JS alerts (and confirms, etc) shouldn't be model to the document canvas (disabling interaction with the canvas, but not browser chrome) rather than the browser itself?
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