The attack seems to have started more than a week ago, and nearly 200,000 web pages have been found to be compromised, most of which are running phpBB. This contrasts yesterday’s attack in that the vast majority of those were active server pages (.ASP). The ASP attacks are different than the phpBB ones in that the payload and method are quite different. Various exploits are used in the ASP attacks, where the phpBB ones rely on social engineering. phpBB mass hacks have occurred in the past, including those done by the Perl/Santy.worm back in 2004.
Here’s a brief video demonstrating how the phpBB attack looks from the end user’s perspective.