Miller will be working with encryption expert Moxie Marlinspike, who was hired by Twitter last year.
"Monday I start on the security team at Twitter. Looking forward to working with a great team there!" Miller tweeted this morning.
Miller told CNET today that he can't talk about his new job until he gets settled in it.
After getting a Ph.D. in mathematics at the University of Notre Dame, Miller worked for five years as a "global network exploitation analyst" for the National Security Agency. He then worked for a financial-services firm and at Independent Security Evaluators and Accuvant.
But it's his hacking and penetration testing skills that have earned him a reputation. Miller has highlighted numerous security flaws within Apple software over the years. One of his most high-profile discoveries was a vulnerability in the mobile version of Safari in 2007, shortly after the first iPhone was released. Additionally, he's been a fixture at the Pwn2Own security contest, in which people vie to gain control of Apple's Mac OS X computers through the built-in Safari Web browser.
More recently, Miller detailed that the low-level system software that ships on all of Apple's recent-model batteries could be hacked, letting would-be attackers theoretically disable the batteries given access to an administrator account. Miller got himself booted from participating in Apple's developer program last year after he released findings of a security hole in the iOS that let applications grab unsigned code from third-party servers that could be added to an app even after it has been approved and is live on Apple's App Store.
In July, Miller demonstrated a way to hijack an Android smartphone via the Near Field Communication (NFC) technology that's turned on by default on the device.