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Monday, 09 July 2018 10:15

Researchers use thermal imaging to guess passwords from keyboards

The thermail residue of the password “passw0rd” on a keyboard 0, 15, 30, and 45 seconds after entry. The thermail residue of the password “passw0rd” on a keyboard 0, 15, 30, and 45 seconds after entry. University of California, Irvine

Researchers at the University of California in Irvine have demonstrated a method whereby sensitive information entered through a keyboard can be retrieved if one has access to the keyboard within a minute of the word(s) being typed.

Thirty users were asked to enter 10 different passwords, both strong and weak, on four different common external keyboards, according to the Slovakian security firm ESET.

The researchers then used a thermal imaging camera to scan the residual heat on the keys which had been used, in order to identify which keys had been pressed.

They then asked non-experts in the field to arrive at the set of pressed keys from the thermal imaging data - which these individuals were able to reliably do.

The subjects were able to retrieve entire sets of key-pressed that were captured by the thermal imaging camera as long as 30 seconds after the first key was used.

The researchers described their method in a paper titled “Thermanator: Thermal Residue-Based Post Factum Attacks On Keyboard Password Entry”.

The data thus obtained was easily leveraged to crack passwords through brute-force attacks.

“Being warm-blooded, human beings naturally prefer environments that are colder than their internal temperature,” the paper says.

“Because of this heat disparity, it is inevitable that we leave thermal residue on numerous objects that we routinely touch, especially, with bare fingers.”

The researchers found that hunt-and-peck typists would be more susceptible to this kind of attack as they left bigger fingerprint and thermal traces, compared to touch typists.

However, attackers need to have access to the keyboards shortly after sensitive data is entered and the thermal imaging camera must have an unrestricted view of the keyboard.

Measures to mitigate against this attack included running one's fingers along a keyboard in order to introduce "thermal noise". Or else, one could use a mouse to select password characters from an on-screen keyboard.

A third method of mitigation was to use gloves or fake nails.


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Sam Varghese

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Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.



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