A website called Gawker was hacked last Sunday and 1.3 million user account passwords compromised that enabled spammers to break into thousands of Twitter accounts where users had used the same passwords.
A file containing those details was then published on a file-sharing site "Bittorrent" by a group "Gnosis". The 500MB file contains data taken from Gawker.
Gawker published a statement on its homepage regarding this matter. They say that although the stored passwords were encrypted, simple passwords are very much vulnerable.
Source: www.bbc.co.uk
