CPSC441 Computer Communications. Ajay Gopinathan Email: email@example.com Homepage: http://pages.cpsc.ucalgary.ca/~agopinat/441/ Office: ICT722 Tel: 403-2109484. Outline. Physical Media Networks under attack: security. Bit: propagates between transmitter/rcvr pairs
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Bit: propagates betweentransmitter/rcvr pairs
physical link: what lies between transmitter & receiver
signals propagate in solid media: copper, fiber, coax
signals propagate freely, e.g., radio
Twisted Pair (TP)
two insulated copper wires
Category 3: traditional phone wires, 10 Mbps Ethernet
Category 5: 100Mbps EthernetPhysical Media
two concentric copper conductors
single channel on cable
multiple channels on cable
HFCPhysical Media: coax, fiber
Fiber optic cable:
no physical “wire”
propagation environment effects:
obstruction by objects
interferencePhysical media: radio
Radio link types:
Let’s work it out!
Malware can get in host from a virus, worm, or trojan horse.
Spyware malware can record keystrokes, web sites visited, upload info to collection site.
Infected host can be enrolled in a botnet, used for spam and DDoS attacks.
Malware is often self-replicating: from an infected host, seeks entry into other hostsBad guys can put malware into hosts via Internet
Hidden part of some otherwise useful software
Today often on a Web page (Active-X, plugin)
infection by receiving object (e.g., e-mail attachment), actively executing
self-replicating: propagate itself to other hosts, usersBad guys can put malware into hosts via Internet
Sapphire Worm: aggregate scans/sec
in first 5 minutes of outbreak (CAIDA, UWisc data)
break into hosts around the network (see botnet)
send packets toward target from compromised hosts
src:B dest:A payloadThe bad guys can use false source addresses
src:B dest:A user: B; password: foo