A major battle is underway for control over hundreds of millions of network-connected digital video recorders, cameras, and other so-called Internet of Things devices. As Ars has chronicled over the past two weeks, hackers are corralling them into networks that are menacing the security news site KrebsOnSecurity and other Web destinations with some of the biggest distributed denial-of-service attacks ever recorded.

Johannes B. Ullrich, a researcher and chief technology officer for the SANS Internet Storm Center, wanted to know just how vulnerable these devices are to remote takeover, so he connected an older DVR to a cable modem Internet connection. What he saw next—a barrage of telnet connection attempts so dizzying it crashed his device—was depressing.

"The sad part is, that I didn't have to wait long," he wrote in a blog post published Monday. "The IP address is hit by telnet attempts pretty much every minute. Instead of having to wait for a long time to see an attack, my problem was that the DVR was often overwhelmed by the attacks, and the telnet server stopped responding. I had to reboot it every few minutes."

A large number of the connection attempts didn't succeed, because the passwords used in the attempted compromise didn't match the default passcode used by his device. Still, "a couple times an hour, someone used the correct password." Fortunately, Ullrich had cordoned off his device to prevent it from harming other Internet citizens. In the background, however, his honeypot showed his device was receiving commands from the hacker mother ship instructing it to scan the Internet for similarly vulnerable devices.

63 passwords is all it takes

The malware that commandeered Ullrich's device is known as Mirai, and it's one of at least two such applications that's unleashing DDoSes of previously unimaginable sizes on targets. Just a year ago, attacks of 620 gigabits per second were only within the reach of nation-sponsored hackers or the most formidable criminal enterprises. Thanks to Mirai and its older counterpart known as Bashlight, they're becoming a point-and-click exercise that relatively unskilled script kiddies can do. As reported Sunday, source code for Mirai was released into the public domain , all but assuring its use will go mainstream.

To build its massive arsenal, according to this technical analysis published Monday, Mirai peppers targeted IoT devices with just 63 different password guesses. Unfortunately, so many devices use one of them as the default login password that Mirai has now become the digital equivalent of a cannon that can knock even large websites offline unless they pay large sums of money to have the attacks blocked. One of the passwords that Ullrich observed being used against the IoT honeypots he monitors is "7ujMko0admin." That just happens to be the default telnet password for a widely used line of IP cameras manufactured by Dahua, one of the most common foot soldiers conscripted into this new breed of DDoS armies. Ullrich has also observed a surge in scans that use the password "xc3511," which is used by default in a generic line of DVRs.

With the release of the Mirai source code, it wouldn't be surprising if hackers update it to include other passwords or expand its reach beyond devices running a form of embedded Linux known as BusyBox. And that could lead to larger and ever more potent DDoSes. Thanks, Internet of Things!