PCBugSquad

Two weeks ago a security research named Dan Kaminksy found a very dangerous flaw in DNS that could allow an attacker to manipulate the information given back by a DNS server.  This attack would allow an attacker to poison a DNS servers cache, so any future requests for the IP address of a host name would instead reply with the attackers chosen IP address rather than the legitimate one.

As part of this announcement, Dan asked that no other security researchers publicly speculate as to the vulnerability in order to not give any black hats, or hackers, the ability to figure the flaw out and use it.  He asked this in order to provide all of the ISPs and companies in the world to update their DNS servers to versions that do not have this flaw.  It turns out, though that another researcher named Halvar Flake may have figured it out.

I wont try to explain it, but you may want to read the blog post i linked above.