With more mass-media attention to the heartbleed bug, we are getting more questions from "normal users" about the heartbleed bug.
The "Heartbleed" bug is not affecting end users using Windows. It does not affect standard Windows browsers (Internet Explorer, Firefox, Chrome). It may affect some selected third party software, but most likely, you do not need to patch anything. The only widely used consumer platform vulnerable is Android 4.1.1, but there isn't much you can do about it but wait for a patch for your phone.
However, it is possible that a web site you used is or was affected by "Heartbleed". The result may be that the password you are using on the site was captured by someone attacking this site. So you may need to change the password that you used on the site.
How do I know if a site is/was vulnerable?
Your best bet is https://lastpass.com/heartbleed/ . They will show you if a site is vulnerable right now, or may have been vulnerable in the past. Tehre is a chance that the site received a new certificate that still uses the old issue date, which can lead to sites being identified as "not fixed".
Should I change my password?
If you think the site was vulnerable, and is no longer vulnerable, then you should change your password. If in doubt, change your password. Changing your password while the site is still vulnerable probably doesn't hurt, but the new password may leak again, so the change may not help.
Should I avoid sites that are still vulnerable?
Yes
I received an e-mail from a site I use asking me to change my password. Should I do so?
First of all: Don't click on any links in this email. Then go to the website and change your password (even if the e-mail was a fake, it doesn't hurt to change your password as long as you are sure you go to the right site). Use the "lastpass" URL above to check if the site is/was vulnerable.
What else should I do?
Standard "safe computing" practices: use difficult to guess passwords, keep your system up to date, use anti-malware, be cautious with links distributed via e-mail.
And how do I explain the problem that caused all this?
XKCD has a great cartoon explaining it: http://imgs.xkcd.com/comics/heartbleed_explanation.png . The short summary: If an SSL connection is idle, heartbeat messages are used to chck if the other side is still listening. For example, the browser sends a message "if you are still alive, reply by sending the 3 letter word 'dog'", and the server replies with "dog". To trigger the bug, the client would send "reply with the 500 letter word 'cow'". Since "cow" only got 3 letters, the server will make up the missing 497 bytes with data from memory, and this data may contain other things the server was working on, like users passwords or private encryption keys.
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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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