As i describe how to scan with nmap in this article,  today i am goiing to show how to scan network in a advanced way.


1 . Layout





Im using python HTTP server in different ports such as on , off, well known and less known ports to demonstrate how this is working


First of all we can discuss how the Transmission Control Protocol Breakdown



Each TCP packet has a section in it’s memory buffer where Control Bits such as URG | ACK | PSH | RST | SYN | FIN can be set.





So How is this URG, ACK, PSH, RST, SYN, FIN works?


here is a small photo that describes all

Image result for how tcp connection is established



Can we change the state SYN to ACK ?


  • yes, that is possible. thats why we need nmap and hping for that



from those tools we can send specific control bits in packets which we are send.


Let's discuss how ip scanners are working


Normally they scanning via icmp


So First of all i scanned my network




so 103 is my ubuntu ip



So simply i disabled icmp in ubuntu



and edit 1 to 0



then again i tried to scan the network




Boom! it not discovering

Then i tried to ping ubuntu machine





it was unsuccessful


SYN Scan


So i was tried to scan using syn scan

#hping : hping -S <address block>
#Nmap : nmap -sS <address block>
#fping : fping -a -g <address block>


hping
-S : Sets the SYN flag getting passed onto the packet

nmap
-sS : SYN flag scan
-sn: ICMP ECHO scan




This is how wireshark looks like when running syn scan


I used firewall to block the 80 port and check syn scan


then enable port 80 in the firewall and tried



Boom! it received SYN,ACK flag



RST scan



ACK Scan





NULL Scan

hping -F -P -U <ip address>

in this command you can see it has multiple Flags





Nmap commands are :
-sX (Xmas scan)
-sN (Null scan)






























































Manusha

Manusha Amal

මගේ තියන අත්දැකීම් මේ බ්ලොග් එක කියවන ඔබට පේනවනේ, ඉතින් ඔයාලට ගැටළුවක් අවොත් මාව Contact කරගන්න පුළුවන්.

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