It's still premature to say you need firewall or antivirus protection for your television set, but a duo of recently diagnosed firmware vulnerabilities in widely used TV models made by two leading manufacturers suggests the notion isn't as far-fetched as many may think.

The most recent bug, found in a wide range of high-definition TVs from Samsung, was disclosed on Thursday by Luigi Auriemma, an Italy-based researcher who regularly finds security flaws in Microsoft Windows, video games, and even the industrial-strength systems used to control dams, gas refineries, and other critical infrastructure. While poking around a Samsung D6000 model belonging to his brother, he inadvertently discovered a way to remotely send the TV into an endless restart mode that persists even after unplugging the device and turning it back on.

"It wasn't even planned," Auriemma told Ars, referring to the most damaging of his two attacks, which rendered the device useless for three days, until he finally found a way to restore it to normal operation. "I wanted only to show a message on the TV when my brother was watching it. He selected the 'deny' choice and boom."

The TV was connected by ethernet cable to a home network, so Auriemma thought it would be funny to use a computer connected to the same network to send it a message that contained a series of custom headers. Without warning, the TV spiraled into an endless loop of restarts. For about five seconds, the device would appear to work correctly, but then would stop responding to commands entered by remote control or through the panel. A few seconds later, the TV would restart and repeat the process. Unplugging the power cord or ethernet cable did nothing. Auriemma had just stumbled upon a crippling denial-of-service attack.

Auriemma said he sees no reason the attack couldn't be carried out over the Internet if the TV had a public IP address and used no filters.

His discovery came two weeks after a separate researcher reported a DoS vulnerability in Sony Bravia TVs. Using the publicly available hping networking tool, Gabriel Menezes Nunes said he was able to seriously disrupt its operation.

"You cannot change the volume, channels or access any function," he wrote in his description of the attack. "After 35 seconds the TV stop(s) working and back. This happens 3 times. At fourth time, the TV shuts down. In less than 3 minutes, the TV is off remotely. It is necessary to turn on the TV physically."

As more and more electronic devices connect to the Internet and home networks, it's likely their internal software will be visited by the same vicious exploits that for years have preyed on products from Microsoft, Adobe, and more recently, Apple.

It's not at all clear if the device manufacturers are up for the challenge of securing their network-connected wares. Auriemma said he discussed the DoS attack with members of Samsung's support team, and they had little advice to offer. His attempts to report the vulnerabilities to support@samsung.com failed as well.

Ars has asked both Samsung and Sony for comment, and this post will be updated if either responds.

Auriemma's attack worked by sending malformed packets to the network port the TV was connected to. He was unable to get the device working, even after speaking to Samsung support personnel, until he finally stumbled on a solution. A service mode that Samsung recommends be used only by service technicians allowed him to clear the configuration memory, making it possible for him to reset the TV.

"It's luck that I suggested the service mode reset to the technicians," he said. The brother service technician, he added, "was ready to load it on his car."

The separate vulnerability discovered by Auriemma also allowed him to crash the TV by tampering with some of the messages his computer sent to the TV. While the device can be restored in a matter of minutes, Auriemma says its possible the attack, which works by replacing the MAC, or media access control, address of his computer with a long string of characters, may exploit a buffer-overflow vulnerability. And if that's the case, it could be possible to remotely execute malicious code on the TVs by carefully appending payloads to the MAC address field.

"That's why (for the moment) I don't want to put my hands again on this stuff," he said. "Maybe another day I will do something and hope to be more 'verbose' the next time. One thing of which I'm sure is that my brother didn't like my joke."

Story updated to reflect that a technician making a service call, not Auriemma's brother, was prepared to load the TV into a car.