Information Networking Security and Assurance Lab National Chung Cheng University Guidelines on Electronic Mail Security

Information Networking Security and Assurance Lab National Chung Cheng University 2 Background The process starts with  Message composition  Transmitted  Mail server processing

Information Networking Security and Assurance Lab National Chung Cheng University 3 Multipurpose Internet Mail Extensions (MIME) RFC 822: transmitting messages containing textual content does not address messages that contain attachments MIME were developed  Audio  Application  Image  Message  Multipart

Information Networking Security and Assurance Lab National Chung Cheng University 4 Mail Transport Standards To ensure reliability and interoperability among various applications Simple Mail Transfer Protocol (SMTP)

Information Networking Security and Assurance Lab National Chung Cheng University 5 Simple Mail Transfer Protocol Extensions

Information Networking Security and Assurance Lab National Chung Cheng University 6 Post Office Protocol developed in 1984 a way to copy messages from the mail server mailbox to the mail client RFC 918, nine commands were originally available for POP

Information Networking Security and Assurance Lab National Chung Cheng University 7 Internet Message Access Protocol

Information Networking Security and Assurance Lab National Chung Cheng University 8 -Related Encryption Standards PGP and S/MIME  Based on public key cryptography symmetric key

Information Networking Security and Assurance Lab National Chung Cheng University 9 Pretty Good Privacy

Information Networking Security and Assurance Lab National Chung Cheng University 10 S/MIME proposed in 1995 by RSA Data Security, Inc. S/MIME version 3

Information Networking Security and Assurance Lab National Chung Cheng University 11 Choosing an Appropriate Encryption Algorithm Required security Required performance System resources Import, export, or usage restrictions Encryption schemes

Information Networking Security and Assurance Lab National Chung Cheng University 12 Key Management difference between PGP and S/MIME  PGP “circle of trust”  S/MIME & some newer PGP “CA”

Information Networking Security and Assurance Lab National Chung Cheng University 13 Hardening the Mail Server Application Securely Installing the Mail Server Securely Configuring Operating System and Mail Server Access Controls  configure access controls  Typical files to which access should be controlled are  use the mail server operating system to limit files accessed by the mail service processes.  directories and files (outside the specified directory tree) cannot be accessed, even if users know the locations of those files.  using a “chroot jail” for the mail server application  To mitigate the effects of certain types of DoS attacks

Information Networking Security and Assurance Lab National Chung Cheng University 14 Protecting from Malicious Code Virus Scanning  at the firewall (application proxy) or mail relay  The benefits  weaknesses

Information Networking Security and Assurance Lab National Chung Cheng University 15 Protecting from Malicious Code Virus Scanning  on the mail server itself  The benefits  weaknesses  Mail servers support the integration of virus scanning at the mail server

Information Networking Security and Assurance Lab National Chung Cheng University 16 Protecting from Malicious Code Virus Scanning  on client hosts  The benefits  weaknesses  Mail servers support the integration of virus scanning at the mail server

Information Networking Security and Assurance Lab National Chung Cheng University 17 Unsolicited Bulk unsolicited commercial (UCE) or spam To control UCE messages open relay blacklists (ORBs)

Information Networking Security and Assurance Lab National Chung Cheng University 18 Miscs Authenticated Mail Relay  benefits  Two methods Secure Access  Most protocols did not initially incorporate any form of encryption or cryptographic authentication  Transport Layer Security protocol  RFC 2595 Enabling Web Access

Information Networking Security and Assurance Lab National Chung Cheng University 19 Using Mail Gateways

Information Networking Security and Assurance Lab National Chung Cheng University 20 Network Element Configuration Router/Firewall Configuration Routers, stateful firewalls, proxy firewalls Which ports Router: network layer (packet filter) firewall