Transcription
Networking 101
“5-minute University” We're just going to cover the basic technologiesthat make up the InternetThere's a lot more content in a ComputerNetworking class that's very valuable, this isjust enough material to be able to talk aboutcybersecurity issuesHopefully not boring for students that alreadytook CS 485/ECE 440/CS 585
Network of two machines10.0.8.1IP address: identifies the machine on the network.Local (10.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12) vs. Internetroutable (e.g., 64.106.21.143).10.0.8.2
What stops me from saying my IP address issomething else (e.g., an IP that belongs tosomeone else) on the same network as me?
man manman ifconfigifconfig less
ARP: Address Resolution Protocol MAC (media access control) address (e.g.,“c4:02:32:6b:00:00”) is supposed to be uniqueto the network interface–Also called a hardware address
(from http://chrissanders.org/packet-captures/)
What stops me from saying my hardwareaddress is something else?
CIDR Classless InterDomain Routing/27 has a netmask of255.255.255.224From Wikipedia
Some notation 192.168.55.0/24 10.0.9.0/24 10.0.8.0/24
Network of .310.0.9.210.0.8.110.0.8.2
IP (Internet Protocol) routingGraphic by Danny Adams
What stops me from saying my IP address isone from a network on the other side of theworld?
tracepath -n uchicago.eduroute -narp -n
TCP/IP TCP Transport Control ProtocolPort: a number that identifies a process or service on the remotemachineSocket: a way for a process on one machine to communicate with aprocess on another machine– TCP is connection-oriented, packets can be lost and retransmitted,delivered out of order, etc.– Can be identified by two port:ipaddress tuplesCompare to UDP, which is the User Datagram ProtocolSee http.pcap example rText Transport Protocol .28HTTP.29
screenCtrl A then C to CreateCtrl A then N for Nexthost www.cs.unm.edunc 64.106.20.27 80(in other terminal.)netstat -tpn less
DNS maps hostnames to IPs andvice versahost 64.106.20.60host wiki.cs.unm.eduman dig
BGP Border Gateway Protocol A path vector protocol that is a lot like adistance vector protocol– Tell your neighbors what routes you know aboutBGP is how Autonomous Systems (ASes) routepackets on the Internet
Network Insecurity ARP, IP, everything else can be spoofedMan-in-the-middle: router pretends to be the host, can doanything–Almost every time you connect to public Wifi–Another example: China's Great CannonMan-on-the-side: more limited, can see packets and insert,but can't modify or drop– Example: NSA QUANTUMWhat are the different places in the network where thesetypes of attacks can be implemented?
Networking 101 “5-minute University” We're just going to cover the basic technologies that make up the Internet There's a lot more content in a Computer Networking class that's very valuable, this is just enou
