A Bias to Insecurity | TechSNAP 223

Posted on: July 16, 2015

The Hacking Team fallout continues with more zero day patches you need to install, a new attack against RC4 might finally kill it & how to save yourself from a DDoS attack.

Plus a great batch of your questions, our answers & much, much more!

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— Show Notes: —

Hacking Team fallout includes more Flash patches

After a number of flash 0-days were found in the data stolen from “Hacking Team”, there has been a mad dash to fix the vulnerabilities before they are actively exploited further
This resulted in nearly back-to-back Adobe Flash updates, confusing some users who thought they had already patched for the vulnerabilities
Additional Coverage: Krebs
Adobe Bulletin – July 8th, released 18.0.0.203
Adobe Advisory – July 10th, Upcoming patch
Adobe Bulletin – July 14th, released 18.0.0.209
This has started quite a few conversations about Flash
Facebook CSO wants Adobe to announce an EOL date for flash ~18-24 months from now
Mozilla has taken the unusual step of disabling flash by default requiring click to activate
Additional Coverage: BBC

New attack against RC4 cipher might finally kill it

RC4 is one of the oldest ciphers still used as part of HTTPS
It was often selected for its lower CPU overhead, but as processors got faster and ssl terminators offloaded the work, this became less of a reason to use RC4
It looked like RC4 would finally die, but then attacks against SSL/TLS that only affected block ciphers emerged: BEAST, Lucky 13, and POODLE
This propelled RC4 back up the priority list
RC4 is also the most compatible cipher, older systems that do not support stronger crypto, all have RC4
RFC 7465 proposed by Microsoft and others, was approved by the IETF and requires that RC4 not be used
Researchers have presented a new paper at the USENIX Security conference that details a new attack against RC4
RC4 is still widely used for HTTPS and also for some types of WiFi
The flaw allows the attacker to steal cookies and other encrypted information in your HTTPS session
This might allow the attack to impersonate / login as you on the site. Posting to your Twitter account, or initiating a transfer from your PayPal account.
“The research behind the attack will be presented at USENIX Security. Summarized, an attacker can decrypt a cookie within 75 hours. In contrast to previous attacks, this short execution time allows us to perform the attack in practice. When we tested the attack against real devices, it took merely 52 hours to successfully perform the attack”
“When the victim visits an unencrypted website, the attacker inserts malicious JavaScript code inside the website. This code will induce the victim to transmit encrypted requests which contain the victim’s web cookie. By monitoring numerous of these encrypted requests, a list of likely cookie values can be recovered. All cookies in this list are tested until the correct one is found.”
Attack Method:
- Step 1: Attacker injects code into victims HTTP stream, causing them to make known requests to a secure site with their cookie
- Step 2: Attacker captures the encrypted requests going to the site secured with RC4
- Step 3: Attacker computes likely cookies and tries each one until they successfully guess the correct cookie
- Step 4: Profit, empty the bank account
“To successfully decrypt a 16-character cookie with a success probability of 94%, roughly 9⋅2^27 encryptions of the cookie need to be captured. Since we can make the client transmit 4450 requests per seconds, this amount can be collected in merely 75 hours. If the attacker has some luck, less encryptions need to be captured. In our demonstration 52 hours was enough to execute the attack, at which point 6.2⋅2^27 requests were captured. Generating these requests can even be spread out over time: they do not have to be captured all at once. During the final step of the attack, the captured requests are transformed into a list of 2^23 likely cookie values. All cookies in this list can be tested in less than 7 minutes.”
“In the paper we not only present attacks against TLS/HTTPS, but also against WPA-TKIP. Our attack against WPA-TKIP takes only an hour to execute, and allows an attacker to inject and decrypt arbitrary packets.”
How does this compare to previous attacks? “The first attack against RC4 as used in TLS was estimated to take more than 2000 hours”
Paper: All Your Biases Belong to Us: Breaking RC4 in WPA-TKIP and TLS