Why is every other web site on the internet slow right now? The answer is most likely the heartbleed vulnerability which was released on April 8th of 2014. The vulnerability is a bug in OpenSSL, the most popular software that is used as a security component for countless other programs including popular web server applications. It is not known how long this has been privately known or how many hackers or other exploiters have known about this bug, but it affects OpenSSL versions that were released from 2012 through versions released as recently as 2014. This means this the impact of this bug is incredibly widespread, and the danger in not immediately correcting the issue is also significant.
The specific danger with the aptly named heartbleed vulnerability is that initiating and maintaining a TCP/IP session with the flawed software compromises the memory of a server 64 bits at a time, including the private key of an SSL certificate used to secure web sites and other secure sessions. This means that one of the likely places an attacker could use the heartbleed vulnerability to compromise the private key for the SSL certificate on a web site, which would allow the attacker to decrypt any intercepted traffic that they captured. In addition to decrypting secure traffic using compromised keys, the attacker could also use the compromised private key to impersonate the service.
The heartbleed vulnerability compromising the private key means that two things need to be done by administrators in order to protect the SSL session from revealing the memory of the server 64 bits at a time. The first is that OpenSSL and any software using OpenSSL as a part of its package will need to be patched to the newly released version (OpenSSL web site is currently down most likely due to overwhelming demand) prevent future compromises of the private key using heartbleed. The second is that every SSL certificate that was exposed to the internet with an application running OpenSSL. It may also be a good idea to instruct users to change passwords on exposed applications since the heartbleed vulnerability apparently has the ability to slowly reveal the entire memory of the compromised server.
So why does this new vulnerability make so many web sites slow? The reason is most likely that engineers are scrambling to update everything and re-key all of the certificates that could be compromised. This means that web servers all over the world are being taken down to run updates, putting a greater strain on the web servers asked to carry the load while those servers are down. It can appear like there is an issue with your internet connection because so many sites run slow, but for the next few days or more things may be running slowly because web servers are being updated as fast as possible.