The “Flashback” virus discovered to have infected more than 600,000 Mac computers earlier this month originated on a series of WordPress blogs, security experts have determined. According to Alexander Gostev, head of the global research and analysis team at Kaspersky, the virus began as a trojan hidden within a fake Adobe software update. In March, however, the malware’s creators repackaged the virus in a “drive-by attack” that infected users’ Apple computers when they visited one of thousands of compromised WordPress blogs.