Microphones Listen To Your… Monitor?

May 25, 2019 by Al Williams 12 Comments

A song by Rockwell, “Somebody’s Watching Me” might be the anthem for the tin foil hat crowd. But a new paper reveals that it might be just as scary to have someone listening to you. Researchers have used common microphones to listen in on computer monitors. The demonstration includes analyzing audio to determine input from virtual keyboards and even a way to tell if people are surfing the web during a Google Hangout session.

Reading monitors based on electronic emissions is nothing new — ask Wim van Eck or read about TEMPEST. What makes this worrisome is that we constantly have live microphones around our computers. Webcams, phones, the latest smart assistant. Even some screens have built-in microphones. According to the paper, you could even pick up data from recorded audio. The paper has three main goals: extract display text, distinguish between different websites on screen, and extracting text entered with a virtual keyboard.

The analysis looked at 31 different screens. There were 12 distinct models from 6 different vendors. They did use a special VGA cable to tap the vertical sync to help manage the data, but they claim this was only an aid and not essential. They also used a high-end sound setup with a 192 kHz sampling rate.

Measuring the sound made by different display patterns was empirical. The authors think the mechanism is from subtle changes in the vibrations of the power supply components due to changes in current consumption. The refresh rate of the monitor also plays a part.

Armed with the proof of concept, the team went on to use an LG V20 cellphone and via a Hangouts call. Imagine if the person on the other end of your call could tell when you were reading Hackaday instead of paying attention to the call.

Different types of monitors need to be learned for best accuracy. It appears that reading small text may have problems, too. Even website detection depends on training. Still, maybe the tin hat people aren’t exactly wrong.

If you want to try your hand at reading the RF emissions, software defined radio is your friend. We’ll be interested to see if anyone duplicates the acoustic method in this paper, though.

A Tool For Spying On Serial Data

May 6, 2015 by Rick Osgood 36 Comments

[Piotr] was working on a recent Arduino project when he ran into a problem. He was having trouble getting his Arduino Pro Mini to communicate with an ESP8266 module. He needed a way to snoop on the back and forth serial communications. Since he didn’t have a specialized tool for this task, [Piotr] ended up building his own.

The setup is pretty simple. You start with a standard serial cable containing the TX, RX, DTR, and GND wires. This cable connects the Arduino to the ESP8266 WiFi module. The TX and RX lines are then tapped into. Each wire is routed to the RX pin of two different serial to USB adapters. This way, the data being sent from the Arduino shows up on one COM port and the data being transmitted from the module shows up on the other.

The next piece of the puzzle was coming up with a way to see the data more clearly. [Piotr] could have opened two serial terminals simultaneously, but this wasn’t ideal because it would be difficult to compare the timing of the data. Instead, [Piotr] spent less than an hour writing his own simple serial terminal. This one connects to two COM ports at the same time and prints the data on the same screen. The data from each COM port is displayed in a separate color to make it easy to differentiate. The schematic and source code to this project can be found on [Piotr’s] website.

Using Facebook Ads To Prank Your Friends

September 19, 2014 by Rick Osgood 38 Comments

Most tech savvy individuals are well aware of the vast amounts of data that social networking companies collect on us. Some take steps to avoid this data collection, others consider it a trade-off for using free tools to stay in touch with friends and family. Sometimes these ads can get a bit… creepy. Have you ever noticed an ad in the sidebar and thought to yourself, “I just searched for that…” It can be rather unsettling.

[Brian] was looking for ways to get back at his new roommate in retaliation of prank that was pulled at [Brian’s] expense. [Brian] is no novice to Internet marketing. One day, he realized that he could create a Facebook ad group with only one member. Playing off of his roommate’s natural paranoia, he decided to serve up some of the most eerily targeted Facebook ads ever seen.

Creating extremely targeted ads without giving away the prank is trickier than you might think. The ad can’t be targeted solely for one person. It needs to be targeted to something that seems like a legitimate niche market, albeit a strange one. [Brian’s] roommate happens to be a professional sword swallower (seriously). He also happens to ironically have a difficult time swallowing pills. naturally, [Brian] created an ad directed specifically towards that market.

The roommate thought this was a bit creepy, but mostly humorous. Slowly over the course of three weeks, [Brian] served more and more ads. Each one was more targeted than the last. He almost gave himself away at one point, but he managed to salvage the prank. Meanwhile, the roommate grew more and more paranoid. He started to think that perhaps Facebook was actually listening in on his phone calls. How else could they have received some of this information? As a happy coincidence, all of this happened at the same time as the [Edward Snowden] leaks. Not only was the roommate now concerned about Facebook’s snooping, but he also had the NSA to worry about.

Eventually, [Brian] turned himself in using another custom Facebook ad as the reveal. The jig was up and no permanent damage was done. You might be wondering how much it cost [Brian] for this elaborate prank? The total cost came to $1.70. Facebook has since changed their ad system so you can only target a minimum of 20 users. [Brian] provides an example of how you can get around the limitation, though. If you want to target a male friend, you can simply add 19 females to the group and then target only males within your group of 20 users. A pretty simple workaround

This prank brings up some interesting social questions. [Brian’s] roommate seemed to actually start believing that Facebook might be listening in on his personal calls for the purposes of better ad targeting. How many other people would believe the same thing? Is it really that far-fetched to think that these companies might move in this direction? If we found out they were already doing this type of snooping, would it really come as a shock to us?

Eavesdropping Encrypted Compressed Voice

June 19, 2008 by Juan Aguilar 1 Comment

A team from Johns Hopkins University has discovered a way to eavesdrop on encrypted voice streams. Voice data like the kind used by Skype for its VoIP service sends encrypted packets of varying sizes for different sounds. The team learned that by simply measureing the size of the packets, they could determine what was being said with a high rate of accuracy. VoIP providers often use a variable bit rate to use bandwidth more efficiently, but it is this compression that makes audio streams vulnerable to eavesdropping.

The team’s software is still in its early stages of development, yet incapable of parsing entire conversations. It is capable, though, of finding pre-determined keywords and inferring common phrases bases on the words it detects. It also has a higher rate of accuracy in identifying long complicated words than short ones. The team’s goal was not to eavesdrop, but to expose the vulnerability; team member [Charles Wright] notes, “we hope we have caught this threat before it becomes too serious.”

[via Schneier on Security]
[photo: altemark]