May 2017
Intermediate to advanced
416 pages
21h 33m
English
Content preview from Nmap: Network Exploration and Security Auditing Cookbook - Second Edition
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How it works...
The arguments -sn -PY scanme.nmap.org tell Nmap to send an SCTP INIT ping scan against the host scanme.nmap.org to determine if it's online. Nmap attempts to initiate a connection to a service by sending a SCTP INIT packet and looks for an ABORT or SCTP ACK message indicating that the service is closed or open correspondingly. Either of those messages give away that the host is online. Let's set the --packet-trace option to see all the packets sent:
SENT (0.0194s) SCTP 192.168.0.14:41354 > 45.33.32.156:80 ttl=50 id=7028 iplen=52 RCVD (0.1604s) SCTP 45.33.32.156:80 > 192.168.0.14:41354 ttl=49 id=0 iplen=36 NSOCK INFO [0.1610s] nsock_iod_new2(): nsock_iod_new (IOD #1) NSOCK INFO [0.1610s] nsock_connect_udp(): UDP connection ...
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