The Bantown hacker group hijacked hundreds of thousands of user accounts at LiveJournal. LiveJournal is an online community ("blogging") with 9,2 millions registered accounts. The hijacking was made possible by stealing "cookies" due to a series of Javascript security flaws in the LiveJournal site.

The hackers said on their site:

In January 2006, Bantownians claimed to have used javascript vulnerabilities in LiveJournal to hijack more than 900,000 of the 1,900,000 active LiveJournal accounts. Fortified by strong cups of coffee, Bantown members created hundreds of dummy member accounts to steal delicious (chocolate-chip) cookies from 16-year-old girls. The energy from these highly nutritious cookies enabled Bantown to crack passwords and break into numerous journals of poor, malnourished LJers.

In order for the account takeovers to end, Bantown demands that Denise Paolucci post on the front page LiveJournal news that LJ has been pwned by Bantown.

Q: Why they did it?
A: For the "LOLs"

Links:
- The full story: http://blogs.washingtonpost.com/securityfix/2006/01/account_hijacki.html
- LiveJournal: http://www.livejournal.com/
- The Bantown hacker group: http://www.encyclopediadramatica.com/index.php/Bantown