computer security compromised by hardware failure computer security compromised by hardware failure is a branch of computer security applied to hardware the objective of computer security includes protection of information and property from theft corruption or natural disaster while allowing the information and property to remain accessible and productive to its intended users such secret information could be retrieved by different ways this article focus on the retrieval of data thanks to misused hardware or hardware failure hardware could be misused or exploited to get secret data this article collects main types of attack that can be lead in a data thief computer security can be comprised by devices such as keyboards monitors or printers thanks to electromagnetic or acoustic emanation for example or by components of the computer such as the memory the network card or the processor thanks to time or temperature analysis for example devices monitor the monitor is the main device used to access data on a computer it has been shown that monitors radiate or reflect data on their environment potentially giving attackers access to information displayed on the monitor electromagnetic emanations video display units radiate narrowband harmonics of the digital clock signals broadband harmonics of the various random digital signals such as the video signal known as compromising emanations or tempest radiation a code word for a us government programme aimed at attacking the problem the electromagnetic broadcast of data has been a significant concern in sensitive computer applications eavesdroppers can reconstruct video screen content from radio frequency emanations compromising reflections what is displayed by the monitor is reflected on the environment the timevarying diffuse reflections of the light emitted by a crt monitor can be exploited to recover the original monitor image this is an eavesdropping technique for spying at a distance on data that is displayed on an arbitrary computer screen including the currently prevalent lcd monitors the technique exploits reflections of the screens optical emanations in various objects that one commonly finds in close proximity to the screen and uses those reflections to recover the original screen content such objects include eyeglasses tea pots spoons plastic bottles and even the eye of the user this attack can be successfully mounted to spy on even small fonts using inexpensive offtheshelf equipment less than 1500 dollars from a distance of up to 10 meters relying on more expensive equipment allowed to conduct this attack from over 30 meters away demonstrating that similar attacks are feasible from the other side of the street or from a closeby building many objects that may be found at a usual workplace can be exploited to retrieve information on a computers display by an outsider the reflections gathered from curved surfaces on closeby objects indeed pose a substantial threat to the confidentiality of data displayed on the screen fully invalidating this threat without at the same time hiding the screen from the legitimate user seems difficult without using curtains on the windows or similar forms of strong optical shielding most users however will not be aware of this risk and may not be willing to close the curtains on a nice day keyboard electromagnetic emanations computer keyboards are often used to transmit confidential data such as passwords since they contain electronic components keyboards emit electromagnetic waves these emanations could reveal sensitive information such as keystrokes the figure below presents how a keystroke is retrieved and what material is necessary diagram presenting all material necessary to detect keystrokes the approach is to acquire the raw signal directly from the antenna and to process the entire captured electromagnetic spectrum thanks to this method four different kinds of compromising electromagnetic emanations have been detected generated by wired and wireless keyboards these emissions lead to a full or a partial recovery of the keystrokes the best practical attack fully recovered 95 of the keystrokes of a ps2 keyboard at a distance up to 20 meters even through walls the four different kinds way of compromising electromagnetic emanations are described below the falling edge transition technique when a key is pressed released or held down the keyboard sends a packet of information known as a scan code to the computer the generalized transition technique the falling edge transition attack is limited to a partial recovery of the keystrokes this is a significant limitation the modulation technique harmonics compromising electromagnetic emissions come from unintentional emanations such as radiations emitted by the clock nonlinear elements crosstalk ground pollution etc determining theoretically the reasons of these compromising radiations is a very complex task the matrix scan technique keyboard manufacturers arrange the keys in a matrix the keyboard controller often an 8bit processor parses columns onebyone and recovers the state of 8 keys at once this matrix scan process can be described as 192 keys some keys may not be used for instance modern keyboards use 104105 keys arranged in 24 columns and 8 rows note that the matrix scan routine loops continuously when no key is pressed we still have a signal composed of multiple equidistant peaks these emanations may be used to remotely detect the presence of powered computers concerning wireless keyboards the wireless data burst transmission can be used as an electromagnetic trigger to detect exactly when a key is pressed while the matrix scan emanations are used to determine the column it belongs to summary some techniques can only target some keyboards this table sums up which technique could be used to find keystroke for different kind of keyboard technique name wired keyboard laptop keyboard wireless keyboard falling edge transition technique yes yes generalized transition technique yes yes modulation technique yes yes matrix scan technique yes yes yes in their paper called compromising electromagnetic emanations of wired and wireless keyboards martin vuagnoux and sylvain pasini tested 12 different keyboard models with ps2 usb connectors and wireless communication in different setups a semianechoic chamber a small office an adjacent office and a flat in a building the table below presents their results type of keyboard number of tested keyboard fett gtt mt mst ps2 7 77 67 47 57 usb 2 02 02 02 22 laptop 2 12 12 02 22 wireless 1 01 01 01 11 acoustic emanations attacks against emanations caused by human typing have attracted interest in recent years in particular works showed that keyboard acoustic emanations do leak information that can be exploited to reconstruct the typed text pc keyboards notebook keyboards are vulnerable to attacks based on differentiating the sound emanated by different keys on average there were only 05 incorrect recognitions per 20 clicks which shows the exposure of keyboard to the eavesdropping using this attack the attack is very efficient taking under 20 seconds per word on a standard pc a 90 or better success rate of finding the correct word for words of 10 or more characters and a success rate of 73 over all the words tested this is a procedure that makes it possible to efficiently uncover a word out of audio recordings of keyboard click sounds video eavesdropping on keyboard while extracting private information by watching somebody typing on a keyboard might seem to be an easy task it becomes extremely challenging if it has to be automated however an automated tool is needed in the case of longlasting surveillance procedures or long user activity as a human being is able to reconstruct only a few characters per minute the paper clearshot eavesdropping on keyboard input from video presents a novel approach to automatically recovering the text being typed on a keyboard based solely on a video of the user typing automatically recognizing the keys being pressed by a user is a hard problem that requires sophisticated motion analysis experiments show that for a human reconstructing a few sentences requires lengthy hours of slowmotion analysis of the video balzarottis analysis is divided into two main phases figure below the first phase analyzes the video recorded by the camera using computer vision techniques for each frame of the video the computer vision analysis computes the set of keys that were likely pressed the set of keys that were certainly not pressed and the position of space characters because the results of this phase of the analysis are noisy a second phase called the text analysis is required the goal of this phase is to remove errors using both language and contextsensitive techniques the result of this phase is the reconstructed text where each word is represented by a list of possible candidates ranked by likelihood diagram presenting steps to go through when detecting keystroke with video input printer acoustic emanations with acoustic emanations an attack that recovers what a dotmatrix printer processing english text is printing is possible it is based on a record of the sound the printer makes if the microphone is close enough to it this attack recovers up to 72 of printed words and up to 95 if knowledge about the text are done with a microphone at a distance of 10cm from the printer after an upfront training phase a in the picture below the attack b in the picture below is fully automated and uses a combination of machine learning audio processing and speech recognition techniques including spectrum features hidden markov models and linear classification a training phase was conducted where words from a dictionary are printed and characteristic sound features of these words are extracted and stored in a database the trained characteristic features was used to recognize the printed english text but this task is not trivial major challenges include identifying and extracting sound features that suitably capture the acoustic emanation of dotmatrix printers compensating for the blurred and overlapping features that are induced by the substantial decay time of the emanations identifying and eliminating wrongly recognized words to increase the overall percentage of correctly identified words recognition rate diagram presenting phases when retrieving data from a printer computer components network interface card timing attack timing attacks enable an attacker to extract secrets maintained in a security system by observing the time it takes the system to respond to various queries ssh is designed to provide a secure channel between two hosts despite the encryption and authentication mechanisms it uses ssh has weaknesses in interactive mode every individual keystroke that a user types is sent to the remote machine in a separate ip packet immediately after the key is pressed which leaks the interkeystroke timing information of users typing below the picture represents the command su processed through a ssh connection network messages sent between the host and the client for the command su numbers are size of network packet in byte a very simple statistical techniques suffice to reveal sensitive information such as the length of users passwords or even root passwords by using advanced statistical techniques on timing information collected from the network the eavesdropper can learn significant information about what users type in ssh sessions memory physical chemistry data remanence problems not only affect obvious areas such as ram and nonvolatile memory cells but can also occur in other areas of the device through hotcarrier effects which change the characteristics of the semiconductors in the device and various other effects which are examined alongside the more obvious memorycell remanence problems electromigration which means to physically move the atom to new locations to physically alter the device itself is another type of attack it involves the relocation of metal atoms due to high current densities a phenomenon in which atoms are carried along by an electron wind in the opposite direction to the conventional current producing voids at the negative electrode and hillocks and whiskers at the positive electrode void formation leads to a local increase in current density and joule heating the interaction of electrons and metal ions to produce thermal energy producing further electromigration effects when the external stress is removed the disturbed system tends to relax back to its original equilibrium state resulting in a backflow which heals some of the electromigration damage in the long term though this can cause device failure but in less extreme cases it simply serves to alter a devices operating characteristics in noticeable ways for example the excavations of voids leads to increased wiring resistance and the growth of whiskers leads to contact formation and current leakage an example of a conductor which exhibits whisker growth due to electromigration is shown in the figure below whisker growth due to electromigration one example which exhibits void formation in this case severe enough to have led to complete failure is shown in this figure void formation due to electromigration temperature contrary to popular assumption drams used in most modern computers retain their contents for several seconds after power is lost even at room temperature and even if removed from a motherboard many products do cryptographic and other securityrelated computations using secret keys or other variables that the equipments operator must not be able to read out or alter the usual solution is for the secret data to be kept in volatile memory inside a tampersensing enclosure security processors typically store secret key material in static ram from which power is removed if the device is tampered with at temperatures below 20c the contents of sram can be frozen it is interesting to know the period of time for which a static ram device will retain data once the power has been removed low temperatures can increase the data retention time of sram to many seconds or even minutes readwrite exploits thanks to firewire maximillian dornseif presented a technique in these slides which let him take the control of an apple computer thanks to an ipod the attacks needed a first generic phase where the ipod software was modified so that it behaves as master on the firewire bus then the ipod had full readwrite access on the apple computer when the ipod was plugged into a firewire port firewire is used by audio devices printers scanners cameras gps etc generally a device connected by firewire has full access readwrite indeed ohci standard firewire standard reads physical requests including physical read physical write and lock requests to some csr registers section 55 are handled directly by the host controller without assistance by system software ohci standard so any device connected by firewire can read and write data on the computer memory for example a device can grab the screen contents just search the memory for strings such as login passwords scan for possible key material search cryptographic keys stored in ram parse the whole physical memory to understand logical memory layout or mess up the memory change screen content change uidgid of a certain process inject code into a process inject an additional process processor cache attack to increase the computational power processors are generally equipped with a cache memory which decreases the memory access latency below the figure shows the hierarchy between the processor and the memory first the processor looks for data in the cache l1 then l2 then in the memory processor cache hierarchy when the data is not where the processor is looking for it is called a cachemiss below pictures show how the processor fetch data when there are two cache levels data a is in the l1cache data a is in the l2cache data a is in the memory unfortunately caches contain only a small portion of the application data and can introduce additional latency to the memory transaction in the case of a miss this involves also additional power consumption which is due to the activation of memory devices down in the memory hierarchy the miss penalty has been already used to attack symmetric encryption algorithms like des timing attack by carefully measuring the amount of time required to perform private key operations attackers may be able to find fixed diffiehellman exponents factor rsa keys and break other cryptosystems against a vulnerable system the attack is computationally inexpensive and often requires only known ciphertext the attack can be treated as a signal detection problem the signal consists of the timing variation due to the target exponent bit and noise results from measurement inaccuracies and timing variations due to unknown exponent bits the properties of the signal and noise determine the number of timing measurements required to for the attack timing attacks can potentially be used against other cryptosystems including symmetric functions privilege escalation see also hardware backdoor a simple and generic processor backdoor can be used by attackers as a means to privilege escalation to get to privileges equivalent to those of any given running operating system loc duflot studied intel processors in the paper cpu bugs cpu backdoors and consequences on security he explains that the processor defines four different privilege rings numbered from 0 most privileged to 3 least privileged kernel code is usually running in ring 0 whereas userspace code is generally running in ring 3 the use of some securitycritical assembly language instructions is restricted to ring 0 code in order to escalate privilege through the backdoor the attacker must activate the backdoor by placing the cpu in the desired state inject code and run it in ring 0 get back to ring 3 in order to return the system to a stable state indeed when code is running in ring 0 system calls do not work leaving the system in ring 0 and running a random system call exit typically is likely to crash the system the backdoors loc duflot presents are simple as they only modify the behavior of three assembly language instructions and have very simple and specific activation conditions so that they are very unlikely to be accidentally activated recent inventions have begun to target these types of processorbased escalation attacks bibliography acoustic asonov d agrawal r 2004 keyboard acoustic emanations ieee symposium on security and privacy 2004 proceedings 2004 proceedings 2004 ieee symposium on security and privacy pp311 citeseerx1011898231 doi101109secpri20041301311 isbn0769521363 issn10816011 zhuang li zhou feng tygar jd 2005 keyboard acoustic emanations revisited proceedings of the 12th acm conference on computer and communications security alexandria virginia usa 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by an ipod pdf pacsec dornseif maximillian 2005 firewire all your memory are belong to us pdf cansecwest processor bug and backdoors duflot loc 2008 cpu bugs cpu backdoors and consequences on security computer security esorics 2008 pdf esorics 08 proceedings of the 13th european symposium on research in computer security computer security lecture notes in computer science 5283 pp580599 doi101007978354088313537 isbn9783540883128 duflot loc 2008 using cpu system management mode to circumvent operating system security functions pdf proceedings of cansecwest pp580599 waksman adam 2010 tamper evident microprocessors pdf proceedings of the ieee symposium on security and privacy oakland california temperature skorobogatov sergei 2002 low temperature data remanence in static ram pdf cambridge uk university of cambridge computer laboratory issn14762986 halderman j alex schoen seth d heninger nadia clarkson william paul william calandrino joseph a feldman ariel j appelbaum jacob felten edward w 2008 lest we remember cold boot attacks on encryption keys pdf proceedings of the usenix security symposium acm new york new york usa 52 5 pp4560 doi10114515064091506429 isbn9781931971607 issn00010782 archived from the original pdf on 20110904 timing attacks song dawn xiaodong wagner david tian xuqing 2001 timing analysis of keystrokes and timing attacks on ssh pdf proceedings of the 10th conference on usenix security symposium washington dc usa usenix association berkeley california usa 10 pp337352 kocher paul c 1996 timing attacks on implementations of diffiehellman rsa dss and other systems advances in cryptology crypto 96 proceedings of the 16th annual international cryptology conference on advances in cryptology crypto 96 lecture notes in computer science 1109 santa barbara california usa springerverlag london uk pp104113 citeseerx1011405024 doi10100735406869759 isbn3540615121 brumley david boneh dan 2003 remote timing attacks are practical pdf proceedings of the 12th conference on usenix security symposium ssym03 washington dc usa usenix association berkeley california usa 12 5 p701 doi101016jcomnet200501010 other balzarotti d cova m vigna g 2008 clear shot eavesdropping on keyboard input from video 2008 ieee symposium on security and privacy sp 2008 security and privacy 2008 sp 2008 ieee symposium on oakland ca pp170183 doi101109sp200828 isbn9780769531687 issn10816011 duflot loc 2007 contribution la scurit des systmes dexploitation et des microprocesseurs pdf in french 