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21-NetSec1 - Network Security Issues Part 1 EE 122...

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Network Security Issues, Part 1 EE 122 - Networking Prof. Vern Paxson November 14, 2011
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Game Plan Two network security lectures – Today: threats at different Internet layers – Wednesday: building secure channels (TLS) Huge landscape – So we will leave a lot undiscussed (feel free to ask!) and omit numerous details Former CS161 students: – You will be bored :-). Feel free to check out. – But: pls don’t answer questions posed for the class
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What We Won’t Be Talking About Layer 7 / Applications presents enormous range of diverse threats – Browser “drive-by” exploits, server vulnerabilities (buffer overflow, SQL injection, XSS, CSRF), spam, phishing, account theft, user tracking … Internet also enables robust, diverse markets that fuel cybercrime – Trade in credit cards, malware installs, stolen accounts, exploit toolkits, spam email lists, “money mules” for cash-out, “bulletproof hosting”, CAPTCHA-solving … – And in general, rapid sharing of knowledge
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Basic Types of Security Goals • Confidentiality : – No one can read our data / communication unless we want them to • Integrity – No one can manipulate our data / processing / communication unless we want them to • Availability – We can access our data / conduct our processing / use our communication capabilities when we want to
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5 Layers 1 & 2: General Threats? Application Transport (Inter)Network Link Physical 7 4 3 2 1 Encoding bits to send them over a single physical link e.g. patterns of voltage levels / photon intensities / RF modulation Framing and transmission of a collection of bits into individual messages sent across a single “subnetwork” (one physical technology)
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6 Physical/Link-Layer Threats: Eavesdropping Also termed sniffing For subnets using broadcast technologies (e.g., WiFi, some types of Ethernet), get it for “free” Each attached system’s NIC can capture any communication on the subnet Some handy tools for doing so o Wireshark o tcpdump / windump o bro For any technology, routers (and switches) can look at / export traffic they forward You can also “tap” a link Insert a device to mirror physical signal Or: just steal it!
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7 Stealing Photons
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8 With physical access to a subnetwork, attacker can Overwhelm its signaling o E.g., jam WiFi’s RF Send messages that violate the Layer-2 protocol’s rules o E.g., send messages > maximum allowed size, disrupt timing synchronization, ignore fairness rules Routers & switches can simply “drop” traffic There’s also the heavy-handed approach … Physical/Link-Layer Threats: Disruption
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9
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10 With physical access to a subnetwork, attacker can create any message on it that they wish Termed spoofing May require root/administrator access to have full freedom Particularly powerful when combined with eavesdropping Because attacker can understand exact state of victim’s communication and craft their spoofed traffic to match it Spoofing w/o eavesdropping = blind spoofing
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  • Spring '11
  • Shenker
  • IP address, Transmission Control Protocol, sequence number, window Urgent pointer, Sequence number Acknowledgment

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