1 2 IP Scan Detetor. 3 ---------------- 4 5 This program is designed to be a passive listener for TCP packets sent to 6 the host. It does not exercise the promiscous mode of interfaces. For 7 routing Unix boxes (and firewalls which route/proxy) this is sufficient to 8 detect all packets going to/through them. 9 10 Upon compiling, a predefined set of "sensitive" ports are configured into 11 the program. Any TCP packets which are seen sent to these ports are counted 12 and the IP# of the sending host recorded, along with the time of the first 13 packet to that port for that IP#. 14 15 After a given number of "hits", it will write the current table of packets 16 out to disk. This number defaults to 10,000. 17 18 To analyze the information written to disk, a sample program called "ipsdr" 19 is used (should but doesn't implement a tree algorithm for storing data) 20 which reads all log files it recognises and totals up the number of ports 21 each host hit. By default, all ports have the same weighting (1). Another 22 group of passes is then made over this table using a netmask of 0xfffffffe, 23 grouping all results which fall under the same resulting IP#. This netmask 24 is then shrunk back to 0, with a output for each level given. This is aimed 25 at detecting port scans done from different hosts on the same subnet (although 26 I've not seen this done, if one was trying to do it obscurely...) 27 28 Lastly, being passive means that no action is taken to stop port scans being 29 done or discourage them. 30 31 Darren 32 darrenr (a] pobox.com 33
Indexes created Sat Apr 11 00:22:22 UTC 2026