Chapter 30 ADP
30.8.1.4 Filtered Port Scans
A filtered port scan may indicate that there were no network errors (ICMP unreachables or TCP RSTs) or responses on closed ports have been suppressed. Active network devices, such as NAT routers, may trigger these alerts if they send out many connection attempts within a very small amount of time. These are some filtered port scan examples.
• | TCP Filtered Portscan | • | UDP Filtered Portscan | • | IP Filtered Portscan |
• | TCP Filtered Decoy | • | UDP Filtered Decoy | • | IP Filtered Decoy |
| Portscan |
| Portscan |
| Portscan |
• | TCP Filtered | • | UDP Filtered Portsweep | • | IP Filtered Portsweep |
| Portsweep |
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• | ICMP Filtered | • | TCP Filtered Distributed | • | UDP Filtered |
| Portsweep |
| Portscan |
| Distributed Portscan |
•IP Filtered Distributed Portscan
30.8.2Flood DetectionFlood attacks saturate a network with useless data, use up all available bandwidth, and therefore make communications in the network impossible.
30.8.2.1 ICMP Flood Attack
An ICMP flood is broadcasting many pings or UDP packets so that so much data is sent to the system, that it slows it down or locks it up.
30.8.2.2 Smurf
A smurf attacker (A) floods a router (B) with Internet Control Message Protocol (ICMP) echo request packets (pings) with the destination IP address of each packet as the broadcast address of the network. The router will broadcast the ICMP echo request packet to all hosts on the network. If there are numerous hosts, this will create a large amount of ICMP echo request and response traffic.
If an attacker (A) spoofs the source IP address of the ICMP echo request packet, the resulting ICMP traffic will not only saturate the receiving network (B), but the network of the spoofed source IP address (C).
Figure 342 Smurf Attack
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