CASPER assault steals info using air-gapped computer’s internal speaker

Scientists at the University of Cyber Stability at Korea College, Seoul, have presented a new covert channel attack named CASPER can leak data from air-gapped pcs to a nearby smartphone at a rate of 20bits/sec.

The CASPER attack leverages the interior speakers inside the target laptop or computer as the information transmission channel to transmit large-frequency audio that the human ear can not hear and convey binary or Morse code to a microphone up to 1.5m away.

The obtaining microphone can be in a smartphone recording sound inside the attacker’s pocket or a notebook in the same room.

Researchers have formerly designed very similar assaults leveraging exterior speakers. Nonetheless, air-gapped, network-isolated techniques employed in essential environments, this sort of as authorities networks, energy infrastructure, and weapon regulate methods, are unlikely to have external speakers.

On the other hand, interior speakers that offer audio feed-back, this kind of as boot-up beeps, are continue to viewed as required, so they are typically present, earning them far better candidates.

Infecting the concentrate on

As is the case with pretty much all magic formula channel attacks concentrating on community-isolated desktops, a rogue employee or a stealthy intruder with physical entry to the concentrate on will have to first infect it with malware.

Though this scenario may well feel impractical or even considerably-fetched, there have been a number of situations of such attacks getting productively carried out in the previous, with notable examples together with the Stuxnet worm, which qualified Iran’s uranium enrichment facility at Natanz, the Agent.BTZ malware that infected a U.S. armed forces foundation, and the Remsec modular backdoor, which secretly gathered information and facts from air-gapped federal government networks for above five several years.

The malware can autonomously enumerate the target’s filesystem, locate data files or file types that match a hardcoded list and try to exfiltrate them.

Extra realistically, it can conduct keylogging, which is far more appropriate for these types of a sluggish details transmission rate.

The malware will encode the info to be exfiltrated from the goal in binary or Morse code and transmit it through the inner speaker utilizing frequency modulation, acquiring an imperceptible ultrasound in a selection amongst 17 kHz and 20 kHz.

CASPER attack diagram
CASPER assault diagram (Korea College)

The benefits

The scientists experimented with the explained model making use of a Linux-based mostly (Ubuntu 20.04) computer system as the concentrate on, and a Samsung Galaxy Z Flip 3 as the receiver, running a essential recorder application with a sampling frequency of up to 20 kHz.

In the Morse code experiment, the scientists established the duration for each little bit to 100 ms and made use of 18 kHz for dots and 19 kHz for the dash. The smartphone was found 50cm away and was capable to decode the sent term “covert.”

In the binary data experiment, the size per little bit was set to 50 ms, transferring zeros at a frequency of 18 kHz and 1s at 19 kHz. A 50 ms commence/conclude bit was also used

Read More