Entries Tagged "cookies"

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New Attack Against ASP.NET

It’s serious:

The problem lies in the way that ASP.NET, Microsoft’s popular Web framework, implements the AES encryption algorithm to protect the integrity of the cookies these applications generate to store information during user sessions. A common mistake is to assume that encryption protects the cookies from tampering so that if any data in the cookie is modified, the cookie will not decrypt correctly. However, there are a lot of ways to make mistakes in crypto implementations, and when crypto breaks, it usually breaks badly.

“We knew ASP.NET was vulnerable to our attack several months ago, but we didn’t know how serious it is until a couple of weeks ago. It turns out that the vulnerability in ASP.NET is the most critical amongst other frameworks. In short, it totally destroys ASP.NET security,” said Thai Duong, who along with Juliano Rizzo, developed the attack against ASP.NET.

Here’s a demo of the attack, and the Microsoft Security Advisory. More articles. The theory behind this attack is here.

EDITED TO ADD (9/27): Three blog posts from Scott Guthrie.

EDITED TO ADD (9/28): There’s a patch.

EDITED TO ADD (10/13): Two more articles.

Posted on September 27, 2010 at 6:51 AM • View Comments

Evercookies

Extremely persistent browser cookies:

evercookie is a javascript API available that produces extremely persistent cookies in a browser. Its goal is to identify a client even after they’ve removed standard cookies, Flash cookies (Local Shared Objects or LSOs), and others.

evercookie accomplishes this by storing the cookie data in several types of storage mechanisms that are available on the local browser. Additionally, if evercookie has found the user has removed any of the types of cookies in question, it recreates them using each mechanism available.

Specifically, when creating a new cookie, it uses the following storage mechanisms when available:

  • Standard HTTP Cookies
  • Local Shared Objects (Flash Cookies)
  • Storing cookies in RGB values of auto-generated, force-cached PNGs using HTML5 Canvas tag to read pixels (cookies) back out
  • Storing cookies in Web History (seriously. see FAQ)
  • HTML5 Session Storage
  • HTML5 Local Storage
  • HTML5 Global Storage
  • HTML5 Database Storage via SQLite

And the arms race continues….

EDITED TO ADD (9/24): WARNING—When you visit this site, it stores an evercookie on your machine.

Posted on September 23, 2010 at 11:48 AM • View Comments

Tracking your Browser Without Cookies

How unique is your browser? Can you be tracked simply by its characteristics? The EFF is trying to find out. Their site Panopticlick will measure the characteristics of your browser setup and tell you how unique it is.

I just ran the test on myself, and my browser is unique amongst the 120,000 browsers tested so far. It’s my browser plugin details; no one else has the exact configuration I do. My list of system fonts is almost unique; only one other person has the exact configuration I do. (This seems odd to me, I have a week old Sony laptop running Windows 7, and I haven’t done anything with the fonts.)

EFF has some suggestions for self-defense, none of them very satisfactory. And here’s a news story.

EDITED TO ADD (1/29): There’s a lot in the comments leading me to question the accuracy of this test. I’ll post more when I know more.

EDITED TO ADD (2/12): Comments from one of the project developers.

Posted on January 29, 2010 at 7:06 AM • View Comments

Flash Cookies

Flash has the equivalent of cookies, and they’re hard to delete:

Unlike traditional browser cookies, Flash cookies are relatively unknown to web users, and they are not controlled through the cookie privacy controls in a browser. That means even if a user thinks they have cleared their computer of tracking objects, they most likely have not.

What’s even sneakier?

Several services even use the surreptitious data storage to reinstate traditional cookies that a user deleted, which is called ‘re-spawning’ in homage to video games where zombies come back to life even after being “killed,” the report found. So even if a user gets rid of a website’s tracking cookie, that cookie’s unique ID will be assigned back to a new cookie again using the Flash data as the “backup.”

Posted on August 17, 2009 at 6:36 AM • View Comments

Privacy Problems with AskEraser

Last week, Ask.com announced a feature called AskEraser (good description here), which erases a user’s search history. While it’s great to see companies using privacy features for competitive advantage, EPIC examined the feature and wrote to the company with some problems:

The first one is the fact that AskEraser uses an opt-out cookie. Cookies are bits of software left on a consumer’s computer that are used to authenticate the user and maintain information such as the user’s site preferences.

Usually, people concerned with privacy delete cookies, so creating an opt-out cookie is “counter-intuitive,” the letter states. Once the AskEraser opt-out cookie is deleted, the privacy setting is lost and the consumer’s search activity will be tracked. Why not have an opt-in cookie instead, the letter suggests.

The second problem is that Ask inserts the exact time that the user enables AskEraser and stores it in the cookie, which could make identifying the computer easier and make it easy for third-party tracking if the cookie were transferred to such parties. The letter recommends using a session cookie that expires once the search result is returned.

Ask’s Frequently Asked Questions for the feature notes that there may be circumstances when Ask is required to comply with a court order and if asked to, it will retain the consumer’s search data even if AskEraser appears to be turned on. Ask should notify consumers when the feature has been disabled so that people are not misled into thinking their searches aren’t being tracked when they actually are, the letter said.

Here’s a copy of the letter, signed by eight privacy organizations. Still no word from Ask.com.

While I have your attention, I want to talk about EPIC. This is exactly the sort of thing the Electronic Privacy Information Center does best. Whether it’s search engine privacy, electronic voting, ID cards, or databases and data mining, EPIC is always at the forefront of these sorts of privacy issues. It’s the end of the year, and lots of people are looking for causes worthy of donation. Here’s EPIC’s donation page; they—well, “we” really, as I’m on the board—can use the support.

Posted on December 21, 2007 at 11:18 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.