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Ns h0503 021104 17 router filtering 361900xx rtr

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NS-H0503-02/1104 17 Router Filtering 36.190.0.xx Rtr src:128.59.10.8 dst:130.207.7.237 Stanford Hey, you shouldn’t be here! Decide whether this packet, with certain source IP address, should come from this side of network. Not standard - local policy.
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NS-H0503-02/1104 18 Router Filtering Very effective for some networks (ISP should always do that!) At least be sure that this packet is from some particular subnet Problems: Hard to handle frequent add/delete hosts/subnets or mobileIP Upsets customers should legitimate packets get discarded Need to trust other routers
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NS-H0503-02/1104 19 TCP Handshake client server SYN seq=x SYN seq=y, ACK x+1 ACK y+1 connection established
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NS-H0503-02/1104 20 TCP Handshake 128.59.10.xx 130.207.xx.xx Rtr Rtr Columbia Georgia Tech 36.190.0.xx Rtr src:128.59.10.8 dst:130.207.7.237 Stanford x seq=y, ACK x+1 The handshake prevents the attacker from establishing a TCP connection pretending to be 128.59.10.8
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NS-H0503-02/1104 21 TCP Handshake Very effective for stopping most such attacks Problems: The attacker can succeed if “y” can be predicted Other DoS attacks are still possible (e.g., TCP SYN-flood)
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NS-H0503-02/1104 22 IP Spoofing & SYN Flood X establishes a TCP connection with B assuming A’s IP address A B X (1 ) S Y N Flood (1 ) S Y N Flood (2) predict B’s TCP seq. (2) predict B’s TCP seq. behavior behavior SYN(seq=m ) ,sr c= A SYN(seq=m ) A (3) (3) (4) (4) SYN(seq=n)ACK(seq=m+1) SYN(seq=n)ACK(seq=m+1) (5) ACK (seq= n+1) (5) ACK (seq= n+1)
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NS-H0503-02/1104 23 Vulnerability A vulnerability (or security flaw) is a specific failure of the security controls.
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