Principles for Software Security

• Secure the weakest link
  Example: social engineering attacks; attacks agains applications vs firewalls
• Defense in depth
  Example: use a VPN and encrypt your data
• Fail securely
  Counterexample: Pressing Esc on the Windows 95/98/Me login screen (with domain login dissabled)
• Principle of least Privilege
  Counterexample: Unix programs running with superooser privileges. Example: sendmail submission user.
• Compartmentalize
  Counterexample: Outlook HTML rendering engine.
• Keep it simple
  Example: choke point e.g. firewall. Counterexample: security protocols, they are complex by neccessity, but flaws are often found years after their introduction.
• Do not volunteer information
  Example:

  $ telnet relay2.ucia.gov smtp
  Trying 198.81.129.194...
  Connected to relay2.ucia.gov.
  Escape character is '^]'.
  220 ain-relay2.net.cia.gov SMTP Ready.
  HELO aueb.gr
  250 (aueb.gr) pleased to meet you.
  

  Counterexample:

  $ telnet mail.aueb.gr smtp
  Trying 195.251.255.142...
  Connected to hermes.aueb.gr.
  Escape character is '^]'.
  220 hermes.aueb.gr ESMTP Sendmail 8.12.9/8.12.9; Fri, 4 Jul 2003 12:53:14 +0300
  HELO aueb.gr
  250 hermes.aueb.gr Hello istlab.dmst.aueb.gr [195.251.253.207], pleased to meet you
  

• Hiding secrets is close to impossible
  Example: DVD DeCSS
• Be reluctant to trust
  Counterexample: downloading software
• Use community resources
  Example: public cryptographic algorithms and their implementations.

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 Last change: Friday, July 4, 2003 12:55 am
 Unless otherwise expressly stated, all original material on this page created by Diomidis Spinellis is licensed under a Creative Commons Attribution-Share Alike 3.0 Greece License.