Protection and Security [supplemental] 1. Network Firewalls

Size: px

Start display at page:

Download "Protection and Security [supplemental] 1. Network Firewalls"

Lisa Walton
8 years ago
Views:

1 Protection and Security [supplemental] 1 Network Firewalls How to connect a trusted computer system to an untrusted network? Put a firewall between the trusted (system or systems) and the untrusted. All traffic must flow through the firewall, which does two things: limits network access (inbound and outbound from secure network) monitors and logs all traffic Traffic restricted by some or all of trusted-network IP address untrusted-network IP address trusted-network port untrusted-network port and may be stateful, e.g., establishing a connection from a trusted machine allows appropriate future traffic

2 Protection and Security [supplemental] 2 Multiple Regions of Trust May be useful to have three regions of trust: trusted, untrusted, and DMZ (demilitarized zone) DMZ typically used for external web servers, etc. Different rules for each path through the firewall ideally, no traffic between DMZ and trusted region, but may not be practical

3 Protection and Security [supplemental] 3 Limitations of Firewalls Firewall needs to be secure Firewalls may be subject to denial-of-service attacks IP addresses can be spoofed Probably can t deal with tunneling attacks port 80 likely to be open to allow HTTP traffic, particularly outbound open inbound: doesn t protect web server from attack (obviously) open inbound: how many things can a web server pass traffic to? open outbound: people piggyback various things on HTTP, creating other points of vulnerability open outbound: a worm or virus can use port 80 to call home

4 Protection and Security [supplemental] 4 Other Firewalls Personal firewall: limit/monitor communication to and from a given host less secure than a physically separate machine Application-proxy firewall: monitor traffic for a particular application-level protocol, e.g., SMTP in principle, functionality that could be in application, e.g., mail server, but isn t

5 Protection and Security [supplemental] 5 Computer-Security Classification U.S. DoD TCSEC (Trusted Computer System Evaluation Criteria) TCB (trusted computing base): those parts of the system that enforce security Four divisions: minimal protection (D), discretionary protection (C), mandatory protection (B), and verified protection (A) One or more classes per division Class D: fails to meet requirements for any other class Class C1: discretionary access control (as in UNIX), user identification Class C2: add fine-grained access control (per-user, not just owner/group/other), audit trails, clearing of storage before reuse, selfprotection of TCB Ordinary commercial systems likely aiming only for C1 or C2

6 Protection and Security [supplemental] 6 Computer-Security Classification Class B1: add mandatory access controls (e.g., confidential/secret/top-secret), maintain sensitivity on storage devices and networks, label output with sensitivity level Class B2: add formal security model, deal with covert channels, more-careful structuring of TCB (including a tamper-proof reference monitor), trusted path for communication between user and TCB Class B3: add specification of users not allowed to access object, reference monitor small enough to be thoroughly tested and analyzed, audit trail for security-related events Class A1: functionally equivalent to B3; add formal design and verification real world intrudes: Informal techniques may be used to identify covert timing channels.

7 Protection and Security [supplemental] 7 Successor to TCSEC: Common Criteria TCSEC now largely obsolete Common Criteria intended to be a logical merge of TCSEC, ITSEC, and CTCPEC Seven Evaluation Assurance Levels (EALs): EAL1 to EAL7 No direct correspondence to TCSEC and EAL1 actually means something, not just failed everything, but EAL3/4 are roughly C2/B1 (collectively) Examples: AIX 5L: EAL4+ HP-UX 11i: EAL4 MacOS : EAL3 Red Hat Enterprise Linux V4 Update 2: EAL 3+ Solaris 9 Release 08/03: EAL4+ Windows XP: EAL4+

DMZ Gateways: Secret Weapons for Data Security

A L I N O M A S O F T W A R E W H I T E P A P E R DMZ Gateways: Secret Weapons for Data Security A L I N O M A S O F T W A R E W H I T E P A P E R DMZ Gateways: Secret Weapons for Data Security EXECUTIVE