rfc2504.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.


RFC 2504                Users' Security Handbook           February 1999


   part in helping an attacker slip through security barriers.  This
   often proves to be an easy stepping-stone onto the protected system
   if the attacker has no authorized access to the system at all.

   Social engineering may be defined, in this context, as the act of
   gaining the trust of legitimate computer users to the point where
   they reveal system secrets or help someone, unintentionally, to gain
   unauthorized access to their system(s).  Using social engineering, an
   attacker may gain valuable information and/or assistance that could
   help break through security barriers with ease.  Skillful social
   engineers can appear to be genuine but are really full of deceit.

   Most of the time, attackers using social enginering work via
   telephone.  This not only provides a shield for the attacker by
   protecting his or her identity, it also makes the job easier because
   the attacker can claim to be a particular someone with more chances
   of getting away with it.

   There are several types of social engineering.  Here are a few
   examples of the more commonly-used ones:

    - An attacker may pretend to be a legitimate end-user who is new to
      the system or is simply not very good with computers.  This
      attacker may approach systems administrators and other end-users
      for help.  This "user" may have lost his password, or simply can't
      get logged into the system and needs to access the system
      urgently.  Attackers have also been known to identify themselves
      as some VIP in the company, screaming at administrators to get
      what they want.  In such cases, the administrator (or it could be
      an end-user) may feel threatened by the caller's authority and
      give in to the demands.

    - Attackers who operate via telephone calls may never even have seen
      the screen display on your system before.  In such cases, the
      trick attackers use is to make details vague, and get the user to
      reveal more information on the system.  The attacker may sound
      really lost so as to make the user feel that he is helping a
      damsel in distress.  Often, this makes people go out their way to
      help.  The user may then reveal secrets when he is off-guard.

    - An attacker may also take advantage of system problems that have
      come to his attention.  Offering help to a user is an effective
      way to gain the user's trust.  A user who is frustrated with
      problems he is facing will be more than happy when someone comes
      to offer some help.  The attacker may come disguised as the
      systems administrator or maintenance technician.  This attacker
      will often gain valuable information because the user thinks that
      it is alright to reveal secrets to technicians.  Site visits may



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RFC 2504                Users' Security Handbook           February 1999


      pose a greater risk to the attacker as he may not be able to make
      an easy and quick get-away, but the risk may bring fruitful
      returns if the attacker is allowed direct access to the system by
      the naive user.

    - Sometimes, attackers can gain access into a system without prior
      knowledge of any system secret nor terminal access.  In the same way
      that one should not carry someone else's bags through Customs, no user
      should key in commands on someone's behalf.  Beware of attackers who
      use users as their own remotely-controlled fingers to type commands on
      the user's keyboard that the user does not understand, commands which
      may harm the system.  These attackers will exploit system software
      bugs and loopholes even without direct access to the system.  The
      commands keyed in by the end-user may bring harm to the system, open
      his own account up for access to the attacker or create a hole to
      allow the attacker entry (at some later time) into the system.  If you
      are not sure of the commands you have been asked to key in, do not
      simply follow instructions.  You never know what and where these could
      lead to...

   To guard against becoming a victim of social engineering, one
   important thing to remember is that passwords are secret.  A password
   for your personal account should be known ONLY to you.  The systems
   administrators who need to do something to your account will not
   require your password.  As administrators, the privileges they have
   will allow them to carry out work on your account without the need
   for you to reveal your password.  An administrator should not have to
   ask you for your password.

   Users should guard the use of their accounts, and keep them for their
   own use.  Accounts should not be shared, not even temporarily with
   systems administrators or systems maintenance techinicians.  Most
   maintenance work will require special privileges which end-users are
   not given.  Systems administrators will have their own accounts to
   work with and will not need to access computer systems via an
   end-user's account.

   Systems maintenance technicians who come on site should be
   accompanied by the local site administrator (who should be known to
   you).  If the site administrator is not familiar to you, or if the
   technician comes alone, it is wise to give a call to your known site
   administrator to check if the technician should be there.  Yet, many
   people will not do this because it makes them look paranoid and it is
   embarrassing to show that they have no, or little trust in these
   visitors.






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RFC 2504                Users' Security Handbook           February 1999


   Unless you are very sure that the person you are speaking to is who he
   or she claims to be, no secret information should ever be revealed to
   such people.  Sometimes, attackers may even be good enough to make
   themselves sound like someone whose voice you know over the phone.  It
   is always good to double check the identity of the person.  If you are
   unable to do so, the wisest thing to do is not to reveal any secrets.
   If you are a systems administrator, there should be security
   procedures for assignment and reassignment of passwords to users, and
   you should follow such procedures.  If you are an end-user, there
   should not be any need for you to have to reveal system secrets to
   anyone else.  Some companies assign a common account to multiple
   users.  If you happen to be in such a group, make sure you know
   everyone in that group so you can tell if someone who claims to be in
   the group is genuine.

Part Three:  End-users self administering a networked computer

   The home user or the user who administers his own network has many of
   the same concerns as a centrally-administered user.  The following is
   a summary of additional advice given in Part Three:

    - Read manuals to learn how to turn on security features, then turn
      them on.
    - Consider how private your data and Email need to be.  Have you
      invested in privacy software and learned how to use it yet?
    - Prepare for the worst in advance.
    - Keep yourself informed about what the newest threats are.

5.  Make Your Own Security Policy

   You should decide ahead of time what risks are acceptable and then
   stick to this decision.  It is also wise to review your decision at
   regular intervals and whenever the need to do so arises.  It may be
   wise to simply avoid downloading any software from the network which
   comes from an unknown source to a computer storing business records,
   other valuable data and data which is potentially damaging if the
   information was lost or stolen.

   If the system has a mixed purpose, say recreation, correspondence
   and some home accounting, perhaps you will hazard some downloading of
   software.  You unavoidably take some risk of acquiring stuff
   which is not exactly what it seems to be.

   It may be worthwhile installing privacy software on a computer if it
   is shared by multiple users.  That way, a friend of a room mate won't
   have access to your private data, and so on.





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6.  Bad Things Happen

   If you notice that your files have been modified or ascertain somehow
   that your account has been used without your consent, you should
   inform your security point-of-contact immediately.  When you do
   not know who your security point-of-contact is, try calling
   your Internet service provider's help desk as a first step.

6.1 How to Prepare for the Worst in Advance

    - Read all user documentation carefully.  Make sure that it is clear
      when services are being run on your computer.  If network services
      are activated, make sure they are properly configured (set all
      permissions so as to prevent anonymous or guest logins, and so
      on).  Increasingly, many programs have networking capabilities
      built in to them.  Learn how to properly configure and safely use
      these features.

    - Back up user data.  This is always important.  Backups are
      normally thought of as a way of ensuring you will not lose your
      work if a hard disk fails or if you make a mistake and delete a
      file.  Backing up is also critical to insure that data cannot be
      lost due to a computer security incident.  One of the most vicious
      and unfortunately common threats posed by computer viruses and
      Trojan Horse programs is erasing a computer's hard disk.

    - Obtain virus checking software or security auditing tools.  Learn
      how to use them and install them before connecting to a public
      network.  Many security tools require that they be run on a
      "clean" system, so that comparisons can be made between the
      present and pristine states.  Thus, it is necessary for some work
      to be done ahead of time.

    - Upgrade networking software regularly.  As new versions of
      programs come out, it is prudent to upgrade.  Security
      vulnerabilities will likely have been fixed.  The longer you wait
      to do this, the greater the risk that security vulnerabilities of
      the products will be become known and be exploited by some network
      assailant.  Keep up to date!

    - Find out who to contact if you suspect trouble.  Does your
      Internet Service Provider have a security contact or Help Desk?
      Investigate this before trouble happens so you won't lose time
      trying to figure it out should trouble occur.  Keep the contact
      information both online and offline for easy retrieval.






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   There are 3 ways to avoid problems with viruses:

      1. Don't be promiscuous

      If at all possible, be cautious about what software you install on
      your system. If you are unaware of or unsure of the origin of a
      program, it is wise not to run it.  Obtain software from trusted
      sources.  Do not execute programs or reboot using old diskettes
      unless you have reformatted them, especially if the old diskettes
      have been used to bring software home from a trade show and other
      potentially security-vulnerable places.

      Nearly all risk of getting infected by viruses can be eliminated
      if you are extremely cautious about what files are stored on your
      computer.  See "The Dangers of Downloading" for more details.

   2. Scan regularly.

      Give your system a regular check-up.  There are excellent
      virus checking and security audit tools for most computer
      platforms available today.  Use them, and if possible, set them to
      run automatically and regularly.  Also, install updates of these
      tools regularly and keep yourself informed of new virus threats.

   3. Notice the unusual.

      It's not true that a difference you cannot detect is no difference
      at all, but it is a good rule of thumb.  You should get used to
      the way your system works.  If there is an unexplainable change
      (for instance, files you believe should exist are gone, or strange
      new files are appearing and disk space is 'vanishing'), you should
      check for the presense of viruses.

   You should take some time to be familiar with computer virus
   detection tools available for your type of computer.  You should use
   an up-to-date tool (i.e. not older than three months).  It is very
   important to test your computer if you have been using shared
   software of dubious origin, someone else's used floppy disks to
   transfer files, and so on.

6.2 What To Do if You Suspect Trouble

   If you suspect that your home computer has a virus, that a malicious
   program has been run, or that a system has been broken into, the
   wisest course of action is to first disconnect the system from all
   networks.  If available, virus detection or system auditing software
   should be used.




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   Checking vital system files for corruption, tampering or malicious
   replacement is very tedious work to do by hand.  Fortunately there are
   many virus detection programs available for PCs and Macintosh
   computers.  There are security auditing programs available for
   UNIX-based computers.  If software is downloaded from the network, it
   is wise to run virus detection or auditing tools regularly.

   If it becomes clear that a home system has been attacked, it is time
   to clean up.  Ideally, a system should be rebuilt from scratch.  This
   means erasing everything on the hard disk.  Next, install the
   operating system and then all additional software the system needs.
   It is best to install the operating system and additional software
   from the original distribution diskettes or CD-roms, rather than from
   backup storage.  The reason for this is that a system may have been
   broken into some time ago, so the backed up system or program files
   may already include some altered files or viruses.  Restoring a system
   from scratch is tedious but worthwhile.  Do not forget to re-install
   all security related fixes you had installed before the security
   incident.  Obtain these from a verified, unsuspicious source.

6.3 Email

   Remember to be careful with saved Email.  Copies of sent or received
   Email (or indeed any file at all) placed in storage provided by an
   Internet service provider may be vulnerable.  The risk is that