What bombastic bob said
What bombastic bob said... my older devices had default username and password, posted on the website. My newer stock devices have the what appears to be a randomly generated password, printed on the device so you can still find it after factory reset. dd-wrt (after some version) used user: admin (or maybe root), password: admin but requires you to set the password first time into the web interface (...which you go into to set up the wifi network name etc. so it's not a step people are going to skip unless they really want a network named dd-wrt with no encryption.)
