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    Lecture 2: September 12, 1995: 6.915 Computer and Network Security Fall Term, 1995

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    Ahmed Hamouda
    1. Physical security is the basis of computer security and involves protecting systems from natural risks like power outages, fires, floods, and human errors, as well as malicious attacks. 2. Backups are an effective solution to many natural risks and should be stored securely off-site. 3. Malicious attacks can include physical access by masquerading or piggybacking individuals, as well as theft of computers, media, or circuitry. Passive and active techniques are used to prevent or detect such attacks.

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    Lecture 2: September 12, 1995: 6.915 Computer and Network Security Fall Term, 1995

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    Ahmed Hamouda
    42 views6 pages
    1. Physical security is the basis of computer security and involves protecting systems from natural risks like power outages, fires, floods, and human errors, as well as malicious attacks. 2. Backups are an effective solution to many natural risks and should be stored securely off-site. 3. Malicious attacks can include physical access by masquerading or piggybacking individuals, as well as theft of computers, media, or circuitry. Passive and active techniques are used to prevent or detect such attacks.

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    1. Physical security is the basis of computer security and involves protecting systems from natural risks like power outages, fires, floods, and human errors, as well as malicious attacks. 2. Backups are an effective solution to many natural risks and should be stored securely off-site. 3. Malicious attacks can include physical access by masquerading or piggybacking individuals, as well as theft of computers, media, or circuitry. Passive and active techniques are used to prevent or detect such attacks.

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    © All Rights Reserved
    Download as PS, PDF, TXT or read online from Scribd
    Download as ps, pdf, or txt
    42 views6 pages

    Lecture 2: September 12, 1995: 6.915 Computer and Network Security Fall Term, 1995

    Uploaded by

    Ahmed Hamouda
    1. Physical security is the basis of computer security and involves protecting systems from natural risks like power outages, fires, floods, and human errors, as well as malicious attacks. 2. Backups are an effective solution to many natural risks and should be stored securely off-site. 3. Malicious attacks can include physical access by masquerading or piggybacking individuals, as well as theft of computers, media, or circuitry. Passive and active techniques are used to prevent or detect such attacks.

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    6.

    915 Computer and Network Security Fall Term, 1995


    Lecture 2 : September 12, 1995
    Lecturer: Ron Rivest Scribe: Chia-Ying (David) Yang

    1 Physical Security
    Physical security is the basis of computer security. We are going to discuss the two
    main uses of physical security: protection against natural risks and malicious attacks.

    1.1 Natural Risks


    These natural risks are the most common threats to computer physical security:

     Power interruption: Power interruption may be hard to recover from. Some-


    times it may result in permanent system damage, since electronic components
    are not designed to absorb sudden power uctuations. UPS (uninterrupted
    power supply), surge protectors, alternative power generators are possible secu-
    rity measures.
    example: Neumann p. 16. AT&T backup battery drain.
     Fire: Smoke detectors and sprinklers are possible security measures. Make sure
    that the water from the sprinklers will not wet the systems, as this may cause
    electrical re and/or water damage (see below.)
     Storm, ood: There are two distinctions to be made between raising waters
    and falling waters. The rst happen in case of ood for example. Systems
    should be placed in high stands and possibly in higher oors of buildings (not
    in the basement.) Falling waters may happen because of leakage during heavy
    storms or because of re alarm sprinklers. The easiest form of protection in this
    case is lots of plastic sheets. Others advocate the use of foam re extinguishers
    instead of water ones .
    example: Neumann p. 56. Passengers were stranded in Sydney's monorail due
    to water damage to control computer.

    1
    2 1 PHYSICAL SECURITY
     Earthquake, Meteor, War: These risks may destroy a whole building. In
    order to quickly restart the computer system rst of all we need up to date
    backups (see section on backups below). Of course the backups should be kept
    in a separate place possibly miles away. In some cases a cold site may be needed,
    i.e. a facility with power, cooling and network connections (i.e., at least phone
    lines), available to install a computer system. For more critical task hot sites
    may be required. A hot site is a facility with a computer system ready to run
    and be used. The cost of maintaining a hot site is high but companies usually
    share the services of a single hot site provider (given the very rarity of use)
    making the cost fairly a ordable.
     Communications interruption: To protect against accidental severance of
    communication lines, duplicate lines at di erent sites are needed.
    example: Neumann p. 17. Beaver chews on cables.
     Operator error: Errors such as co ee spills and accidental le deletion are
    very common.
    example: Chernobyl accident, 1986.
     Software/hardware error
    example: Neumann p. 68. Therac-25 chemotherapy machine fried several pa-
    tients due to software bugs.
    Backups: The most e ective solution to many of these natural risks is to create
    backups. Many types of backups are possible{ daily, weekly, and monthly, as well
    as full, incremental, and di erential. Backups can be used either for quick restart or
    restoration of damaged systems, as well as for record keeping and tracking purposes.
    Backups should be separately stored in a secure place away from the system. Backups
    should be regularly tested to make sure that the data on the backups are intact.
    Also backups may contain sensitive information so they should be protected since
    they provide an attacker with a potential entry point to private data other than the
    computer system itself.

    1.2 Malicious Attacks


    1.2.1 Physical access control
    Walls and fences de ne the security perimeter, while guards and locks enforce ac-
    cess control policy. Only authorized users may enter the perimeter. Possible security
    leaks include:
    1.2 Malicious Attacks 3

     Masquerading: A person disguised as an authorized user. This can be done


    using forged IDs or pretending to be a repair man.
     Piggy-backing: A person who enters the security perimeter by following an
    authorized user.
     Lock-picking: Any locked can be picked. Sometimes there is substantial sav-
    ings over combinatorial brute-force.
     Visual/auditory access: An unauthorized person can gain passwords using
    binoculars, telephone bugs, etc.

    Possible solutions to these attacks include:

     Safes, doors with special locks


    example: Hotel doors with special access keys based on a sequence of random
    numbers.
     Motion detectors
    example: the movie Sneakers.

    1.2.2 Protecting computer systems


    To prevent theft, computers can be locked to desks or other immovable furnitures.
    In addition, locks on computers or on media readers can render a stolen computer
    unusable.

    1.2.3 Protecting media


    Possible security leaks include:

     Dumpster diving: Shredded documents may yield secrets such as passwords


    and con dential information.
     Magnetic storage media: Deleted information can often be undeleted.
    example: Oil company that reads consultants' tapes before writing on them.

    Possible solutions to these attacks include:


    4 1 PHYSICAL SECURITY
     Clearing, purging, destroying: Clearing overwrites data multiple times with
    some character. Purging eradicates data using, for example, ultraviolet light for
    EEPROMs or degaussing for magnetic media. Destroying completely destroys
    the media by, for example, burning or melting.
     Zeroize disk on memory allocation
    Another facet of media protection is protection against software piracy. United States
    piracy rate is estimated at 35%, which results in $15.2 billion in loss per year. Software
    companies have devised these copy protection methods:

     Bad tracks at known places on disk


     A dongle is a special hardware that attaches to, for example, the serial port.
    It contains circuitry which is needed to run the software.
     Serial number/manual text check
     Network address/CPU check

    Often the most e ective copy protection is no protection at all. By lowering the price
    of the software or by providing excellent support services, many users are willing to
    buy their own copy of the software.

    1.2.4 Protecting devices and circuitry


    A device or circuit can use a key for short-term protection or incorporate protection
    into the design for long-term protection. There are two protection techniques: passive
    (preventive) and active (counter measures).

    1.2.4.1 Passive protection techniques


     Potting circuitry in epoxy makes it hard to remove components for study.
     Special \connoisseur" coating
    example: A layer of alumina, silicon bits, and even sodium coating may be
    on chip, making it hard to etch. The sodium is even reactive, causing further
    damage when it is exposed. These special coatings are usually expensive.
    1.2 Malicious Attacks 5

     Special 3D geometry makes it hard for etching or milling to etch down to


    the circuit evenly...
     Stress glassed substrate on which the circuitry is built can shatter when the
    enemy tries to remove components for study.
     Fake circuits that do nothing can confuse the enemy.
     Programmable circuits makes it hard for visual circuitry study (if program-
    ming is done with, say, ion implants or polysilicon fuses.
    Possible security leaks for passive techniques include:
     Diagnostic circuits built into some circuits may give away its functions (e.g.
    the ability to scan out all registers on the chip).
     Underside of chip is often neglected, and may provide an access route (etch
    away from backside).
     Optical or infrared viewing

    1.2.4.2 Active protection techniques


     Pressurized containers: circuitry can be disabled when a loss in pressure is
    sensed.
     Wires through epoxy potting can detect damage to epoxy potting.
     Self-destruct device can destroy the circuitry if its security is compromised.
    Possible security leaks for active techniques include:
     Fast attacks by the enemy may destroy counter measures before they are
    activated.
     Slow attacks such as liquid nitrogen may disable circuitry while leaving the
    charges detectable.
     Power usage and timing may give away sensitive information about function-
    ality of chip.
     Zeroizing memory may not be enough, since long-term charge storage may
    cause physical changes such as ion migration.
    6 3 READINGS
    1.3 Electromagnetic Radiations
    Computers (in particular their screens and their communication lines) emit the elec-
    tromagnetic radiation. It is possible for an attacker to make use of such emissions in
    order to create privacy breaches.
    Computer CRT signals can be picked up from afar with simple, cheap equipment.
    Communications cable active tapping can be detected, but inductive tapping is much
    harder. Fiber optic cables can be tapped through bending, nicking, or placing in
    high-refractive liquids, which may cause some light to escape. In addition, the power
    lines also radiate signal energy.
    It is possible to shield a computer, but it is dicult and expensive to do it well.
    Tempest is the name of the program of the U.S. Government under which computer
    equipment is certi ed as not emitting detectable signals. One approach is to surround
    circuits with metal shielding. Shielding the whole computer is hard, since the shield
    should enclose everything (including the screen ...) A good compromise is to use a
    ne copper mesh in front of the screen. Sometimes entire computer rooms or entire
    buildings are shielded.
    The best electromagnetic radiation security is a orded when the equipment
    is switched o .
    Peter Swinbank

    2 Principles
    The following principles can be gathered from what we learned about physical secu-
    rity:
     If information is in physical form, it can be accessed by the enemy.
     Physical protection is at the foundation of computer and network security.

    3 Readings
    Chapter 12 of the textbook deals with physical security. Also Peter Neumann's
    book Computer Related Risks (which is quoted in these notes) is a good collection of
    computer risks due to lack of adequate physical protection.

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