The NSA’s software does this by measuring the amount of time the network takes to send different types of data from one computer to another and raising a red flag if something takes too long, according to the patent filing.
Other researchers have looked into this problem in the past and proposed a technique called distance bounding, but the NSA patent takes a different tack, comparing different types of data travelling across the network. “The neat thing about this particular patent is that they look at the differences between the network layers,” said Tadayoshi Kohno, an assistant professor of computer science at the University of Washington.
The technique could be used for purposes such as detecting a fake phishing Web site that was intercepting data between users and their legitimate banking sites, he said. “This whole problem space has a lot of potential, [although] I don’t know if this is going to be the final solution that people end up using.”
Entries Tagged "phishing"
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Based in Europe, the Rock Phish group is a criminal collective that has been targeting banks and other financial institutions since 2004. According to RSA, they are responsible for half of the worldwide phishing attacks and have siphoned tens of millions of dollars from individuals’ bank accounts. The group got its name from a now discontinued quirk in which the phishers used directory paths that contained the word “rock.”
The first sign the group was expanding operations came in April, when it introduced a trojan known alternately as Zeus or WSNPOEM, which steals sensitive financial information in transit from a victim’s machine to a bank. Shortly afterward, the gang added more crimeware, including a custom-made botnet client that was spread, among other means, using the Neosploit infection kit.
Soon, additional signs appeared pointing to a partnership between Rock Phishers and Asprox. Most notably, the command and control server for the custom Rock Phish crimeware had exactly the same directory structure of many of the Asprox servers, leading RSA researchers to believe Rock Phish and Asprox attacks were using at least one common server. (Researchers from Damballa were able to confirm this finding after observing malware samples from each of the respective botnets establish HTTP proxy server connections to a common set of destination IPs.)
Last week’s dramatic rescue of 15 hostages held by the guerrilla organization FARC was the result of months of intricate deception on the part of the Colombian government. At the center was a classic man-in-the-middle attack.
In a man-in-the-middle attack, the attacker inserts himself between two communicating parties. Both believe they’re talking to each other, and the attacker can delete or modify the communications at will.
The Wall Street Journal reported how this gambit played out in Colombia:
“The plan had a chance of working because, for months, in an operation one army officer likened to a ‘broken telephone,’ military intelligence had been able to convince Ms. Betancourt’s captor, Gerardo Aguilar, a guerrilla known as ‘Cesar,’ that he was communicating with his top bosses in the guerrillas’ seven-man secretariat. Army intelligence convinced top guerrilla leaders that they were talking to Cesar. In reality, both were talking to army intelligence.”
This ploy worked because Cesar and his guerrilla bosses didn’t know one another well. They didn’t recognize one anothers’ voices, and didn’t have a friendship or shared history that could have tipped them off about the ruse. Man-in-the-middle is defeated by context, and the FARC guerrillas didn’t have any.
And that’s why man-in-the-middle, abbreviated MITM in the computer-security community, is such a problem online: Internet communication is often stripped of any context. There’s no way to recognize someone’s face. There’s no way to recognize someone’s voice. When you receive an e-mail purporting to come from a person or organization, you have no idea who actually sent it. When you visit a website, you have no idea if you’re really visiting that website. We all like to pretend that we know who we’re communicating with—and for the most part, of course, there isn’t any attacker inserting himself into our communications—but in reality, we don’t. And there are lots of hacker tools that exploit this unjustified trust, and implement MITM attacks.
Even with context, it’s still possible for MITM to fool both sides—because electronic communications are often intermittent. Imagine that one of the FARC guerrillas became suspicious about who he was talking to. So he asks a question about their shared history as a test: “What did we have for dinner that time last year?” or something like that. On the telephone, the attacker wouldn’t be able to answer quickly, so his ruse would be discovered. But e-mail conversation isn’t synchronous. The attacker could simply pass that question through to the other end of the communications, and when he got the answer back, he would be able to reply.
This is the way MITM attacks work against web-based financial systems. A bank demands authentication from the user: a password, a one-time code from a token or whatever. The attacker sitting in the middle receives the request from the bank and passes it to the user. The user responds to the attacker, who passes that response to the bank. Now the bank assumes it is talking to the legitimate user, and the attacker is free to send transactions directly to the bank. This kind of attack completely bypasses any two-factor authentication mechanisms, and is becoming a more popular identity-theft tactic.
There are cryptographic solutions to MITM attacks, and there are secure web protocols that implement them. Many of them require shared secrets, though, making them useful only in situations where people already know and trust one another.
The NSA-designed STU-III and STE secure telephones solve the MITM problem by embedding the identity of each phone together with its key. (The NSA creates all keys and is trusted by everyone, so this works.) When two phones talk to each other securely, they exchange keys and display the other phone’s identity on a screen. Because the phone is in a secure location, the user now knows who he is talking to, and if the phone displays another organization—as it would if there were a MITM attack in progress—he should hang up.
Zfone, a secure VoIP system, protects against MITM attacks with a short authentication string. After two Zfone terminals exchange keys, both computers display a four-character string. The users are supposed to manually verify that both strings are the same—”my screen says 5C19; what does yours say?”—to ensure that the phones are communicating directly with each other and not with an MITM. The AT&T TSD-3600 worked similarly.
This sort of protection is embedded in SSL, although no one uses it. As it is normally used, SSL provides an encrypted communications link to whoever is at the other end: bank and phishing site alike. And the better phishing sites create valid SSL connections, so as to more effectively fool users. But if the user wanted to, he could manually check the SSL certificate to see if it was issued to “National Bank of Trustworthiness” or “Two Guys With a Computer in Nigeria.”
No one does, though, because you have to both remember and be willing to do the work. (The browsers could make this easier if they wanted to, but they don’t seem to want to.) In the real world, you can easily tell a branch of your bank from a money changer on a street corner. But on the internet, a phishing site can be easily made to look like your bank’s legitimate website. Any method of telling the two apart takes work. And that’s the first step to fooling you with a MITM attack.
Man-in-the-middle isn’t new, and it doesn’t have to be technological. But the internet makes the attacks easier and more powerful, and that’s not going to change anytime soon.
This essay originally appeared on Wired.com.
This is a big deal:
At issue is a growing trend in which ISPs subvert the Domain Name System, or DNS, which translates website names into numeric addresses.
When users visit a website like Wired.com, the DNS system maps the domain name into an IP address such as 18.104.22.168. But if a particular site does not exist, the DNS server tells the browser that there’s no such listing and a simple error message should be displayed.
But starting in August 2006, Earthlink instead intercepts that Non-Existent Domain (NXDOMAIN) response and sends the IP address of ad-partner Barefruit’s server as the answer. When the browser visits that page, the user sees a list of suggestions for what site the user might have actually wanted, along with a search box and Yahoo ads.
The rub comes when a user is asking for a nonexistent subdomain of a real website, such as http://webmale.google.com, where the subdomain webmale doesn’t exist (unlike, say, mail in mail.google.com). In this case, the Earthlink/Barefruit ads appear in the browser, while the title bar suggests that it’s the official Google site.
The hacker could, for example, send spam e-mails to Earthlink subscribers with a link to a webpage on money.paypal.com. Visiting that link would take the victim to the hacker’s site, and it would look as though they were on a real PayPal page.
Kaminsky demonstrated the vulnerability by finding a way to insert a YouTube video from 80s pop star Rick Astley into Facebook and PayPal domains. But a black hat hacker could instead embed a password-stealing Trojan. The attack might also allow hackers to pretend to be a logged-in user, or to send e-mails and add friends to a Facebook account.
Earthlink isn’t alone in substituting ad pages for error messages, according to Kaminsky, who has seen similar behavior from other major ISPs including Verizon, Time Warner, Comcast and Qwest.
Salesforce.com has finally acknowledged what security experts have suspected for weeks: that a Salesforce.com employee had his company credentials stolen
in a phishing scam, and criminals have been using names and e-mail addresses from Salesforce’s customer list to conduct other highly targeted phishing attacks, including the recent round of fake e-mails apparently from the Federal Trade Commission.” In such hightly targeted attacks, the AV companies are at a loss—they have little chance of quickly developing signatures for threats that only reach a few thousand victims.
Here’s a interesting paper from Carnegie Mellon University: “An Inquiry into the Nature and Causes of the Wealth of Internet Miscreants.”
The paper focuses on the large illicit market that specializes in the commoditization of activities in support of Internet-based crime. The main goal of the paper was to understand and measure how these markets function, and discuss the incentives of the various market entities. Using a dataset collected over seven months and comprising over 13 million messages, they were able to categorize the market’s participants, the goods and services advertised, and the asking prices for selected interesting goods.
Really cool stuff.
Unfortunately, the data is extremely noisy and so far the authors have no way to cross-validate it, so it is difficult to make any strong conclusions.
The presidential campaigns’ tactic of relying on impulsive giving spurred by controversial news events and hyped-up deadlines, combined with a number of other factors such as inconsistent Web addresses and a muddle of payment mechanisms creates a conducive environment for fraud, says Soghoian.
“Basically, the problem here is that banks are doing their best to promote safe online behavior, but the political campaigns are taking advantage of the exact opposite,” he says. “They send out one million e-mails to people designed to encourage impulsive behavior.”
He characterizes the current state of security of the presidential campaigns’ online payment systems as a “mess.”
“It’s a disaster waiting to happen,” he says.
Fraudsters could easily send out e-mails and establish Web sites that mimic the official campaigns’ sites and similarly send out such e-mails that would encourage people to “donate” money without checking for the authenticity of the site.
He has a point, but it’s not new to online contributions. Fake charities and political organizations have long been problems. When you get a solicitation in the mail for “Concerned Citizens for a More Perfect Country”—insert whatever personal definition you have for “more perfect” and “country”—you don’t know if the money is going to your cause or into someone’s pocket. When you give money on the street to someone soliciting contributions for this cause or that one, you have no idea what will happen to the money at the end of the day.
In the end, contributing money requires trust. While the Internet certainly makes frauds like this easier—anyone can set up a webpage that accepts PayPal and send out a zillion e-mails—it’s nothing new.
Two studies. The first one looks at social phishing:
Test subjects received an e-mail with headers spoofed so that it appeared to originate from a member of the subject’s social network. The message body was comprised of the phrase “hey, check this out!” along with a link to a site ostensibly at Indiana University. The link, however, would direct browsers to www.whuffo.com, where they were asked to enter their Indiana username and password. Control subjects were sent the same message originating from a fictitious individual at the university.
The results were striking: apparently, if the friends of a typical college student are jumping off a cliff, the student would too. Even though the spoofed link directed browsers to an unfamiliar .com address, having it sent by a familiar name sent the success rate up from 16 percent in controls to over 70 percent in the experimental group. The response was quick, with the majority of successful phishes coming within the first 12 hours. Victims were also persistent; all responses received a busy server message, but many individuals continued to visit and supply credentials for hours (one individual made 80 attempts).
Females were about 10 percent more likely to be victims in the study, but male students were suckers for their female friends, being 15 percent more likely to respond to phishes from women than men. Education majors had the smallest disparity between experimental and control members, but that’s in part because those majors fell for the control phish half the time. Science majors had the largest disparity—there were no control victims, but the phish had an 80 percent success rate in the experimental group.
Okay, so no surprise there. But this is interesting research into how who we trust can be exploited. If the phisher knows a little bit about you, he can more effectively target your friends.
And we all know that some men are suckers for what women tell them.
Another study looked at the practice of using the last four digits of a credit-card number as an authenticator. Seems that people also trust those who know the first four digits of their credit-card number:
Jakobsson also found a problem related to the practice of credit card companies identifying users by the last four digits of their account numbers, which are random. From his research, it turns out people are willing to respond to fraudulent e-mails if the attacker correctly identifies the first four digits of their account numbers, even though the first four are not random and are based on who issued thecard.
“People think [the phrase] ‘starting with’ is just as good as ‘ending with,’ which of course is remarkable insight,” he said.
Another attack comes to mind. You can write a phishing e-mail that simply guesses the last four digits of someone’s credit-card number. You’ll only be right one in ten thousand times, but if you send enough e-mails that might be enough.
EDITED TO ADD (8/14): Math typo fixed.
Sidebar photo of Bruce Schneier by Joe MacInnis.