We leave Thermal residue on various objects that include common input devices such as the keyboard, which we use to enter sensitive details.
Three researchers from the University of California published a paper describing their study on how the thermal residues collected from users who entered both weak and strong password can be recovered as late as 1 minute after entry.
If you are Hunt-and-peck typist then it is more dangerous, it is a method where the user searches for the key location in keyboard and pressing each key only with their index fingers.
Researchers conducted an experiment with “30 users entering 10 unique passwords (both weak and strong) on 4 popular commodity keyboards. Results show that entire sets of key-presses can be recovered by non-expert users.”
Attack Scenario – Thermanator attack
Thermanator attack is an insider attack, where an attacker needs to have a physical attack to the keyboard to collect thermal residues.
1. Victim enter’s a genuine password to log-in.
2. The victim may step away from the workplace.
3. An attacker using thermal imaging camera can harvest information from the keyboard.
4. By using the heatmap of the image, attackers can locate the keystrokes typed.
Researchers say Hunt-and-Peck Typists are highly vulnerable, they result in greater
heat transfer, due to longer contact duration with a larger contact area. For Touch typists, two factors confuse their thermal residues and make passwords harder to harvest.
Mitigation Against Thermanator attack
1. Users to swipe their hands along the keyboard after password entry.
2. On-screen keyboard.
3. Users could wear insulating gloves or rubber thimblettes over their fingers during password entry.
Researchers concluded that “Work described in this paper sheds some light on understanding the thermodynamic relationship between human fingers and external computer keyboards. In particular, it exposes the vulnerability of standard password-based systems to an adversarial collection of thermal emanations.”
More technical details can be found in the paper “Thermanator: Thermal Residue-Based Post Factum Attacks On Keyboard Password Entry” published by researchers.