Gmail accounts hacked via unpatched hole
By Scott Spanbauer
Exploits allowing hackers to break into Gmail accounts are likely to occur, if they're not already circulating, after security researchers released details of a hole that Google has reportedly declined to patch.
There are steps you can take to reduce the risk of using a webmail account, but it appears that the usual tricks won't solve the Gmail problem until Google fixes the software.
The weakness that researchers say afflicts Gmail, a free e-mail service hosted by Google, belongs to a class of attacks known as cross-site request forgery (CSRF, pronounced "sea surf").
Besides Gmail, CSRF holes affecting YouTube, Netflix, and NYTimes.com have also been found and repaired in the past. CSRF attacks use security flaws in cookies, password requests, and other interactive Web components to intercept communications between your browser and a Web site's server.
The first report of the Gmail problem within security circles was written by Vicente Aguilera Díaz of Internet Security Auditors (ISA) on July 30, 2007. The next day, ISA issued an alert and included a proof of concept illustrating how the exploit could be used to change a Gmail account password.
After more than a year during which, according to ISA, Google was repeatedly contacted privately about the problem researchers publicly released a detailed description of the exploit on March 3, 2009, according to a Secure Computing article.
The magazine quoted an unnamed Google spokesman as saying, "We've been aware of this report for some time, and we do not consider this case to be a significant vulnerability, since a successful exploit would require correctly guessing a user's password within the period that the user is visiting a potential attacker's site."
Considering that an automated attack can test thousands of passwords in a matter of seconds, you might not be very reassured by Google's position. Many PC users select weak passwords that consist of common names or dictionary words, leaving them susceptible to brute-force discovery. And the general release of the CSRF technique makes it easy for hackers to write opportunistic code, if actual exploits aren't already in the wild.
The March 3 public disclosure should not be confused with an earlier Gmail CSRF flaw that was first reported on Jan. 1, 2007. Google repaired that problem by the following day, according to a blog post by software consultant Hari Gottipati.
CSRF attacks — which are also referred to as session-riding — are different from the more-widely known cross-site scripting (XSS) exploits. XSS holes allow a malicious Web site that's open in one browser window to inject JavaScript into another site's page that's open in a separate window or tab. Once the unwanted script is running on a PC, the code can try to collect private data and passwords and transmit them back to the attacker's server.
XSS vulnerabilities have recently been discovered and patched in many browsers and on many sites, including Yahoo Mail and Hotmail as well as Gmail......(continues)
Gmail's sea-surf hole can't be closed by SSL
Some reports on the Web, such as an article at Softpedia.com, say using https during your Gmail sessions blocks CSRF attacks on the service.
Unfortunately, that's not the case for this Gmail hole, according to ISA's Aguilera. In an e-mail interview conducted in Aguilera's native Spanish, he said the flaw allows a hacker to take advantage of an encrypted session (the following is my translation from the original language):
* "In this vulnerability, the attacker causes the victim to generate, invisible to the victim, a request to the server (in which request the victim's authenticated session cookie is also transmitted).
"When the server receives the request, it sees that it comes from an authenticated session (the victim's), and thus is unable detect that, in reality, the request was instigated by the attacker.
"In other words, it's as if the victim/user actually created the request to the server, and the fact that the communication is encrypted is unrelated and doesn't prevent the attack."
Using https does prevent traffic sniffing and so-called man-in-the-middle attacks, so you should enable it regardless of whether Gmail's CSRF hole is ever patched....(continues)
