rfc2504.txt

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   is very difficult to determine for sure who sent a message.  This
   means that Email itself is a not a suitable way to conduct many types
   of business.  It is very easy to forge an Email message to make it
   appear to have come from anyone.

   Another security issue you should consider when using Email is
   privacy.  Email passes through the Internet from computer to
   computer.  As the message moves between computers, and indeed as it
   sits in a user's mailbox waiting to be read, it is potentially
   visible to others. For this reason, it is wise to think twice before
   sending confidential or extremely personal information via Email.
   You should never send credit card numbers and other sensitive data
   via unprotected Email.  Please refer to "The Wires Have Ears".

   To cope with this problem, there are privacy programs available, some
   of which are integrated into Email packages.

   One service many Email users like to use is Email forwarding.  This
   should be used very cautiously.  Imagine the following scenario:

      A user has an account with a private Internet Service Provider and
      wishes to receive all her Email there.  She sets it up so that her
      Email at work is forwarded to her private address.  All the Email
      she would receive at work then moves across the Internet until it
      reaches her private account.  All along the way, the Email is
      vulnerable to being read.  A sensitive Email message sent to her
      at work could be read by a network snoop at any of the many stops
      along the way the Email takes.

   Note that Email sent or received at work may not be private.  Check
   with your employer, as employers may (in some instances) legally both
   read your Email and make use of it.  The legal status of Email
   depends on the privacy of information laws in force in each country.





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   Many mail programs allow files to be included in Email messages.  The
   files which come by Email are files like any other.  Any way in which
   a file can find its way onto a computer is possibly dangerous.  If
   the attached file is merely a text message, fine.  But it may be more
   than a text message.  If the attached file is itself a program or an
   executable script, extreme caution should be applied before running
   it.  See the section entitled "The Dangers of Downloading".

3.4 Passwords

   Passwords may be easily guessed by an intruder unless precautions are
   taken.  Your password should contain a mixture of numbers, upper and
   lower case letters, and punctuation.  Avoid all real words in any
   language, or combinations of words, license plate numbers, names and
   so on.  The best password is a made-up sequence (e.g., an acronym
   from a phrase you won't forget), such as "2B*Rnot2B" (but don't use
   this password!).

   Resist the temptation to write your password down.  If you do, keep
   it with you until you remember it, then shred it!  NEVER leave a
   password taped onto a terminal or written on a whiteboard.  You
   wouldn't write your PIN code on your automated teller machine (ATM)
   card, would you?  You should have different passwords for different
   accounts, but not so many passwords that you can't remember them.
   You should change your passwords periodically.

   You should also NEVER save passwords in scripts or login procedures
   as these could be used by anyone who has access to your machine.

   Be certain that you are really logging into your system.  Just
   because a login prompt appears and asks you for your password does
   not mean you should enter it.  Avoid unusual login prompts and
   immediately report them to your security point-of-contact.  If you
   notice anything strange upon logging in, change your password.

   Unless precautions have been taken to encrypt your password when it
   is sent over the network, you should, if possible, use "one-time
   passwords" whenever you log in to a system over a network.  (Some
   applications take care of that for you.)  See "The Wires Have Ears"
   for more information on the risks associated with logging in over a
   network.

3.5 Viruses and Other Illnesses

   Viruses are essentially unwanted pieces of software that find their
   way onto a computer.  What the virus may do once it has entered its
   host, depends on several factors:  What has the virus been programmed
   to do?  What part of the computer system has the virus attacked?



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   Some viruses are 'time bombs' which activate only when given a
   particular condition, such as reaching a certain date.  Others remain
   latent in the system until a particular afflicted program is
   activated.  There are still others which are continually active,
   exploiting every opportunity to do mischief.  A subtle virus may
   simply modify a system's configuration, then hide.

   Be cautious about what software you install on your system.  Use
   software from "trusted sources", if possible.  Check your site policy
   before installing any software:  Some sites only allow administrators
   to install software to avoid security and system maintenance
   problems.

   Centrally-administered sites have their own policy and tools for
   dealing with the threat of viruses.  Consult your site policy or find
   out from your systems administrator what the correct procedures are
   to stay virus free.

   You should report it if a virus detection tool indicates that your
   system has a problem.  You should notify your site's systems
   administrators as well as the person you believe passed the virus to
   you.  It is important to remain calm.  Virus scares may cause more
   delay and confusion than an actual virus outbreak.  Before announcing
   the virus widely, make sure you verify its presence using a virus
   detection tool, if possible, with the assistance of
   technically-competent personnel.

   Trojan Horse programs and worms are often categorized with viruses.
   Trojan Horse programs are dealt with in the "What Program is This,
   Anyway?" section.  For the purposes of this section, worms should be
   considered a type of virus.

3.6 Modems

   You should be careful when attaching anything to your computer, and
   especially any equipment which allows data to flow.  You should get
   permission before you connect anything to your computer in a
   centrally-administered computing environment.

   Modems present a special security risk.  Many networks are protected
   by a set of precautions designed to prevent a frontal assault from
   public networks.  If your computer is attached to such a network, you
   must exercise care when also using a modem.  It is quite possible to
   use the modem to connect to a remote network while *still* being
   connected to the 'secure' net.  Your computer can now act as a hole
   in your network's defenses.  Unauthorized users may be able to get
   onto your organization's network through your computer!




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   Be sure you know what you are doing if you leave a modem on and set
   up your computer to allow remote computers to dial in.  Be sure you
   use all available security features correctly.  Many modems answer
   calls by default.  You should turn auto-answer off unless you are
   prepared to have your computer respond to callers.  Some 'remote
   access' software requires this.  Be sure to turn on all the security
   features of your 'remote access' software before allowing your
   computer to be accessed by phone.

   Note that having an unlisted number will not protect you from someone
   breaking into your computer via a phone line.  It is very easy to
   probe many phone lines to detect modems and then launch attacks.

3.7 Don't Leave Me...

   Do not leave a terminal or computer logged in and walk away.  Use
   password-locked screensavers whenever possible.  These can be set up
   so that they activate after the computer has been idle for a while.

   Sinister as it may seem, someone coming around to erase your work is
   not uncommon.  If you remained logged in, anyone can come by and
   perform mischief for which you may be held accountable.  For example,
   imagine the trouble you could be in for if nasty Email were sent to
   the president of your company in your name, or your account were used
   to transfer illegal pornography.

   Anyone who can gain physical access to your computer can almost
   certainly break into it.  Therefore, be cautious regarding who you
   allow access to your machine.  If physically securing your machine is
   not possible, it is wise to encrypt your data files kept on your
   local hard disk.  If possible, it is also wise to lock the door to
   one's office where the computer is stored.

3.8 File Protections

   Data files and directories on shared systems or networked file
   systems require care and maintenance.  There are two categories of
   such systems:

    - Files to share

      Shared files may be visible to everyone or to a restricted group
      of other users.  Each system has a different way of specifying
      this.  Learn how to control sharing permissions of files and
      implement such control without fail.






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    - Protected files

      These include files that only you should have access to, but
      which are also available to anyone with system administrator
      privileges.  An example of this are files associated with the
      delivery of Email.  You don't want other users to read your Email,
      so make sure such files have all the necessary file permissions
      set accordingly.

3.9 Encrypt Everything

      Additionally, there are files that are private.  You may have files
      which you do not wish anyone else to have access to.  In this case,
      it is prudent to encrypt the file.  This way, even if your network is
      broken into or the systems administrator turns into Mr. Hyde, your
      confidential information will not be available.  Encryption is also
      very important if you share a computer.  For example, a home computer
      may be shared by room mates who are friends but prefer to keep their
      Email and financial information private.  Encryption allows for
      shared yet private usage.

      Before you encrypt files, you should check your site's security
      policy.  Some employers and countries expressly forbid or restrict
      the storing and/or transferring of encrypted files.

      Be careful with the passwords or keys you use to encrypt files.
      Locking them away safely not only helps to keep them from prying eyes
      but it will help you keep them secure too; for if you lose them, you
      will lose your ability to decrypt your data as well!  It may be wise
      to save more than one copy.  This may even be required, if your
      company has a key escrow policy, for example.  This protects against
      the possibility that the only person knowing a pass phrase may leave
      the company or be struck by lightning.

      Whilst encryption programs are readily available, it should be noted
      that the quality can vary widely.  PGP (which stands for "Pretty Good
      Privacy") for example, offers a strong encryption capability.  Many
      common software applications include the capability to encrypt data.
      The encryption facilities in these are typically very weak.

      You should not be intimidated by encryption software.  Easy-to-use
      software is being made available.

3.10 Shred Everything Else

      You would be surprised what gets thrown away into the waste-paper
      basket:  notes from meetings, old schedules, internal phone lists,
      computer program listings, correspondence with customers and even



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      market analyses.  All of these would be very valuable to competitors,
      recruiters and even an overzealous (hungry?) journalist looking for a
      scoop.  The threat of dumpster diving is real - take it seriously!
      Shred all potentially useful documents before discarding them.

      You should also be aware that deleting a file does not erase it in
      many cases.  The only way to be sure that an old hard disk does not
      contain valuable data may be to reformat it.

3.11 What Program is This, Anyway?

      Programs have become much more complex in recent years.  They are
      often extensible in ways which may be dangerous.  These extensions
      make applications more flexible, powerful and customizable.  They
      also open the end-user up to all sorts of risks.

    - A program may have "plug-in" modules.  You should not trust the
      plug-ins simply because you are used to trusting the programs
      they plug into.  For example: Some web pages suggest that the
      user download a plug-in to view or use some portion of the web
      page's content.  Consider: What is this plug-in?  Who wrote it?
      Is it safe to include it in your web browser?

    - Some files are "compound documents".  This means that instead of
      using one single program, it will be necessary to run several
      programs in order to view or edit a document.  Again, be careful
      of downloading application components.  Just because they
      integrate with products which are well-known does not mean that
      they can be trusted.  Say, you receive an Email message which can
      only be read if you download a special component.  This component
      could be a nasty program which wipes out your hard drive!