Network Reconnaissance

9 important questions on Network Reconnaissance

What are the two fundamental approaches in the first step of reconnaissance?

Passive and active information gathering.

What would be the first step of active reconnaissance?

Obtain a high-level overview of the organization's systems and to obtain a list of the hosts contained within.

How is the global IP address space managed?

Managed by IANA, that has divided up and allocated pools of available addresses to the five Regional Interest Registries (RIR).
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How do you call a reversed DNS lookup?

Zone transfer (usually not configured).

What is a common technique to get router-level maps when doing network reconnaissance

Traceroute utility!

What can be concluded if with a traceroute lookup a probe is consistently returned within 2 milliseconds?

That with an approximate link speed of 200.000km/s the total distance to this device and back must be within 400km

Give 3 examples of inverse scans, why are these unusual scans used?

NULL scan (TCP packet without any control bits), FIN scan (TCP segment flagging the end of a TCP connection), XMAS scan (urgency buffer push and connection end are set to true). Only work if RFC is correctly implemented.
 
Is used because it might be possible to stay under the radar and remain undetected.

What are the two disadvantages of a TCP connection scan, what is an alternative?

1) It takes resources for the client, reducing the speed at which a client may scan a network.
2) Operating system will pass the connection to the network application, thus potentially leave some trace in the log files.

Alternative is a SYN scan.

What 3 characteristic can be analysed to look what operating system is used?

  1. TTL value in IP header
  2. TCP window size
  3. Initial TCP acknowledgement number

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