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network_security_assesment [2009/06/08 03:37]
k2patel
network_security_assesment [2017/03/31 21:58]
k2patel [TCP Port Scanning]
Line 443: Line 443:
 Media video stream and PowerPoint presentation from [[ http://​www.blackhat.com/​html/​bh-usa-00/​bh-usa-00-speakers.html | Link]] Media video stream and PowerPoint presentation from [[ http://​www.blackhat.com/​html/​bh-usa-00/​bh-usa-00-speakers.html | Link]]
  
-[[96]]+=== Low-Level IP Assessment === 
 +Tools such as Nmap, Hping2, and Firewalk perform low-level IP assessment. 
 + 
 +Insight into the following areas of a network can be gleaned through low-level IP assessment:​ 
 + 
 +  * Uptime of target hosts (by analyzing the TCP timestamp option) 
 +  * TCP services that are permitted through the firewall (by analyzing responses to TCP and ICMP probes) 
 +  * TCP sequence and IP ID incrementation (by running predictability tests) 
 +  * The operating system of the target host (using IP fingerprinting) 
 + 
 +The TCP timestamp option is defined in RFC 1323. 
 +== Analyzing Responses to TCP Probes == 
 +A TCP probe always results in one of four responses. These responses potentially\\ 
 +allow an analyst to identify where a connection was accepted, or why and where it\\ 
 +was rejected, dropped, or lost: 
 +  * TCP SYN/ACK 
 +If a SYN/ACK packet is received, the port is considered open. 
 +  * TCP RST/ACK 
 +If an RST/ACK packet is received, the probe packet was rejected by either the\\ 
 +target host or an upstream security device (e.g., a firewall with a reject rule in its policy). 
 +  * ICMP type 3 code 13 
 +If an ICMP type 3 code 13 message is received, the host (or a device such as a\\ 
 +firewall) has administratively prohibited the connection according to an Access Control List (ACL) rule. 
 +  * Nothing 
 +If no packet is received, an intermediary security device silently dropped it. 
 + 
 +==== Simple tcpdump ==== 
 +dumping traffic with pcap_filter 
 +<code bash> 
 +tcpdump -i eth2 -s 0 -w /​tmp/​mar_2017.pcap host 192.168.1.86 
 +</​code>​ 
 + 
 +Reading pcap output file 
 +<code bash> 
 +tcpdump -qns 0 -X -r /​tmp/​mar_2017.pcap 
 +</​code>​ 
network_security_assesment.txt · Last modified: 2017/03/31 21:58 by k2patel