ECE Prof. John A. Copeland fax Office: Klaus or call for office visit, Chapter 10a - Firewalls 3/10/2013

2 Computer System Evolution Central Data Processing System: - with directly attached peripherals (card reader, magnetic tapes, line printer). Local Area Networks: - connects PC ’ s (in “ terminal emulation ” mode), remote terminals (next building) and mini-computers. Premises Network: - connects LANs and LAN-attached devices to each other. Enterprise-wide Network: - leased data lines (T1, DS-3) connect various offices. Internet Connectivity: - initially for , now for Web access, e- commerce, music and video downloads, social networking, tele-commuting, Web and video conferencing, distance learning,.... Makes the world accessible, but now the world also has access to you.

3 Agency Virtual Private Network LANs at Agency Offices across Georgia State WWW Gateway State Internet Citizens Contractors City & County Governments Agency Gateway & Web Server Non-Agency State Server Private Virtual Connection Agency Server Schools Libraries Kiosks Connectivity Provided by the Georgia Backbone Network Other Agencies WWW Firewalls

Agency Firewall - Protects Agency Subnets from Unwanted Connections Agency Firewall - Protects Agency Subnets from Unwanted Connections Subnet 1 Subnet 2 Gate- way WAN Firewalls (and many routers) can reject: Packets with certain source and destination addresses Packets with certain high-level protocols (UDP, Telnet) Proxy Servers - for specific applications messages assembled and inspected, then passed to internal server machine. Prevent Cyber Loafing - Using the Internet for fun and personal business (not very effective). Gate- way 4

5 Application Layer (HTTP) Transport Layer (TCP,UDP) Network Layer (IP) E'net Data Link Layer Ethernet Phys. Layer Network Layer E'net Data Link Layer E'net Phys. Layer Network Layer Web Server Browser Router-Firewall can drop packets based on source or destination, ip address and/or port Application Layer (HTTP) Transport Layer (TCP,UDP) Network Layer (IP) Token Ring Data-Link Layer Token Ring Phys. Layer IP Address IP Address Port 80 Port Segment No. Token Ring Data Link Layer Token Ring Phys. Layer

Application Layer (HTTP, FTP, TELNET, SMTP) Transport Layer (TCP, UDP) Network Layer (IP) E'net Data Link Layer E'net Phys. Layer Transport Layer (TCP, UDP) Network Layer (IP) E'net Data Link Layer E'net Phys. Layer Process Transport or App.-Layer Gateway, or Proxy Application Layer (HTTP(HTTP, FTP, TELNET, SMTP) Transport Layer (TCP,UDP) Network Layer (IP) TR Data Link Layer TR Phys. Layer Transport Layer (TCP, UDP) Network Layer (IP) TR Data Link Layer TR Phys. Layer 6

Policy No outside Web access. Outside connections to Public Web Server Only. Prevent Web-Radios from eating up the available bandwidth. Prevent your network from being used for a Smuft DoS attack. Prevent your network from being tracerouted or Ping scanned. Firewall Setting Drop all outgoing packets to any IP, Port 80 Drop all incoming TCP SYN packets to any IP except 130:207: , port 80 Drop all incoming UDP packets - except DNS and Router Broadcasts. Drop all ICMP packets going to a “ broadcast ” address ( or ). Drop all incoming ICMP, UDP, or TCP echo- request packets, drop all packets with TTL < 5. 7

Firewall Attacks IP Internal-Address Spoofing Source Routing (External Spoof) Tiny Fragment Attacks 2nd-Fragment Probes SYN-ACK Probes Internal Outbound Hacking Firewall Defense Drop all incoming packets with local source address. Drop all IP packets with Source-Routing Option. Drop all incoming packet fragments with small size. Assemble IP fragments (hard work), or at least *. Be “ Stateful ” -keep track of TCP outgoing SYN packets (start of all TCP connections). Drop all outgoing packets which do not have an "internal" source IP address. 8 * Fragments after the first one have no transport header (no way to tell if it is TCP, UDP, ICMP,..., or determine port numbers. Firewall must at least keep a temporary list of approved IP ID-Numbers based on the first fragment decision.

A Network Firewall is a single point that a Network Administrator can control, even if individual computers are managed by workers or departments Over half of corporate computer misfeasance is caused by employees who are already behind the main firewall. Solution 1 - isolate subnets with firewalls (usually routers or Ethernet switches with “ filter ” capabilities). Protect Finance Department from Engineering Department [Problem: internal network is much higher bit rate, firewalls more expensive]. Solution 2 - implement host-based firewalls to limit access except on certain TCP/UDP ports from specific hosts or subnets. Must be centrally managed to be economical. Solution 3 – Use a Intruder Detection System that divides the network into zones, and reports unauthorized cross-zone connections. 9

Stateful Firewall Local PC ip1 External Host ip2 TCP SYN establishes “state” (ip1,ip2,tcp, 33489,80) TCP SYN-ACK or RESET or relatedICMP established “state” (ip1,ip2,tcp, 33489,80) TCP ACK’s established “state” (ip1,ip2,tcp, 33489,80) TCP or UDP or ICMP Not part of an established “state” 10

# iptables -L -n Chain INPUT (policy DROP) target prot opt source destination ACCEPT tcp / /0 ACCEPT tcp / /0 ACCEPT all / /0 tcp dpt:22 ACCEPT tcp /0 tcp dpt:22 ACCEPT tcp / /0 ACCEPT udp / /0 tcp dpt:22 ACCEPT tcp / /0 tcp dpt:22 ACCEPT tcp / /0 tcp dpt:22 DROP all / /0 Chain FORWARD (policy DROP) target prot opt source destination DROP all -- anywhere anywhere Chain OUTPUT (policy DROP) target prot opt source destination ACCEPT icmp -- anywhere /24 ACCEPT icmp -- anywhere anywhere state RELATED,ESTABLISHED 11 A “ -n ” option speeds up iptables because it stops reverse lookups. Also beneficial for “ route ”, “ netstat ”, ….

$ ufw status numbered Status: active To Action From [ 1] 8822/tcp ALLOW IN [ 2] Anywhere ALLOW IN /25 [ 3] 8822/tcp ALLOW IN [ 4] 8822/tcp ALLOW IN /16 [ 5] 8822/tcp ALLOW IN /16 [ 6] Anywhere DENY IN Anywhere $ ufw insert 1 allow proto tcp from /16 to any port 8822 Rule Inserted $ ufw activate (changes iptables configuration) Uncomplicated Firewall (UFW) for Ubuntu (LINUX) 12

Internet Router with NAT Host Web Client Host Host Web Server port 80 FTP Server port 21 Web Server To :80 from :x To :80 from :y To :y from :80 To :x from : Local Web client accessing an external Web server x & y are high number ephemeral client ports. Simple NATs, use x=y NAT - Network Address Translation

Internet Router with NAT Host Host Host Host Web Server port 80 FTP Server port 21 FTP Client To :y from :21 To : x from :21 To : 21 from :x To :21 from :y External FTP client accessing a local FTP server Forwarding Table Port 80 ->.10 Port 21 ->.30

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16 Home Routers allow incoming connections based on server port New Home Routers also allow port translation (e.g., > 22)

Combined Firewalls and IDS (see also: IBM Proventia

Protocol Anomaly Detection WatchGuard Transparent Application layer proxies examine entire connection data streams, identifying protocol anomalies and discarding harmful or questionable information. In addition, WatchGuard firewalls perform: * Packet Handling - prevents packets from entering the network until they are reassembled and examined. * Packet Reassembly - reassembles packet fragments to prevent fragment overlap attacks such as Teardrop and other Layer 3 protocol anomaly based attacks. Signature Element Analysis Rather than using signatures that precisely identify specific attacks, WatchGuard systems look at what any attack of a certain type (e.g., ) must do to succeed (e.g., auto-execute an attachment). With rule sets, you can choose to allow or deny traffic, or even deny all traffic from a source for a specific period. In addition to rigorous rule sets, the firewall processes policy-based configurations, and management subsystems perform state and content analysis. These processes protect against entire known and unknown attack classes, and can narrow the vulnerability window without having to make you wait for updated attack-specific signatures. Behavior-Based Analysis Although behavior-based intrusion detection is a relatively new technology, WatchGuard has mechanisms in place within the firewall to identify known attack behaviors, such as: * Port scans and probes * Spoofing * SYN flood attacks * DoS and DDoS attacks * The misuse of IP options such as source routing from 18

Network Operations * Resolve network performance issues in minutes * Provides enterprise network visibility down to user level * Troubleshoots network incidents at 1/3 the time of point solutions * Analyzes NetFlow / sFlow to facilitate capacity planning and traffic engineering Network Security * Detects attacks that bypass signature based, perimeter defenses * Leverages flow data, including packet capture, to reduce security risks by 90% * Enforces policies and assures compliance with agent-free user identity tracking * Delivers scalable, robust security and risk management from 19 (also see