flow-dscan(1)						      General Commands Manual						     flow-dscan(1)

NAME

       flow-dscan -- Detect scanning and other suspicious network activity.

SYNOPSIS

       flow-dscan  [-bBhlmpwW]	 [-d  debug_level]   [-D iplist_depth]	[-s state_file]  [-i input_filter]  [-L suppress_list]	[-o output_filter]
       [-O excessive_octets]  [-P excessive_flows]  [-S port_scan_trigger]  [-t ager_timeout]

DESCRIPTION

       The flow-dscan utility is used to detect suspicious activity such as port scanning, host scanning, and flows with unusually high octets	or
       packets.   A source and destination suppress list is supported to help prevent false alarms due to hosts such as nameservers or popular web
       servers that exchange traffic with a large number of hosts.  Alarms are logged to syslog or stderr.  The internal state of  flow-dscan  can
       be saved and loaded to allow for interrupted operation.

       flow-dscan  will  work  best  if  configured  to  only watch only inbound or outbound traffic by using the input or output interface filter
       option.

       The host scanner works by counting the length of the destination IP hash chain.	If it goes above 64, then the  src  is	considered  to	be
       scanning.

       The  port scanner works by keeping a bitmap of the destination port number < 1024 per destination IP.  If it goes above 64, the src is con-
       sidered to be port scanning the destination.

       When a src has been flagged as scanning it will not be reported again until the record is aged out and enough flows trigger it again.

       A SIGHUP signal will instruct flow-dscan to reload the suppress list.

       A SIGUSR1 signal will instruct flow-dscan to dump its internal state.

OPTIONS

       -b	 Do not detach and run in the background.  Alerts go to stderr.

       -B	 Do not detach and run in the background.  Alerts go to syslog.

       -d debug_level
		 Enable debugging.

       -D iplist_depth
		 Depth of IP host list for detecting host scanning.

       -h	 Display help.

       -i input_filter
		 Input interface filter list.

       -I output_filter
		 Output interface filter list.

       -l	 Load state from /var/tmp/dscan.state or the filename specified with -s.

       -L suppress_list
		 Basename of suppress files.  There are two suppress files for input and output traffic.  The suppress file syntax is

		 IP_address protocol source_port destination_port

		 A '-' can be used as a wildcard in the protocol, source_port, and destination_port fields.  Only a single protocol,  source_port,
		 and destination_port is supported per IP address.

       -m	 Multicast address filter.  Use to ignore multicast addresses.

       -O excessive_octets
		 Trigger an alert if a flow is processed with the octets field exceeding excessive_octets.

       -p	 Dump state to /var/tmp/dscan.state or the filename specified with -s.

       -P excessive_packets
		 Trigger an alert if a flow is processed with the packets field exceeding excessive_packets.

       -s statefile
		 State filename.  Defaults to /var/tmp/dscan.state

       -S port_scan_trigger
		 Number of ports a IP address must have used to be considered scanning.

       -t ager_timeout
		 How long to keep flows around.  Default to 90000.  This is measured in flows processed.

       -T excessive_time
		 Trigger an alert if a flow is processed with the End-Start field exceeding excessive_time.

       -w	 Filter (ignore) candidate inbound www traffic, ie IP protocol 6, source port 80, and destination port > 1023.

       -W	 Filter (ignore) candidate outbound www traffic, ie IP protocol 6, destination port 80, and source  port > 1023.

EXAMPLES

       In  a  topology where 25 is the only output interface run flow-dscan over the data in /flows/krc4.  Ignore www and multicast traffic, store
       the internal state in dscan.statefile on exit.  Use empty suppress list files dscan.suppress.src and dscan.suppress.dst.  The  output  pro-
       duced  by  flow-dscan typically must be manually inspected by using flow-filter and flow-print.	Many of the alerts will be false until the
       suppress lists are populated for the local environment.

	 flow-cat /flows/krc4 | flow-dscan -I25 -b -m -s dscan.statefile -p -W

BUGS

       The ager should automatically become more aggressive when a low memory condition exists.

       There is no upper limit on the number of records that can be allocated.	If the ager is not running often enough the host will be  run  out
       of memory.

AUTHOR

       Mark Fullmer maf@splintered.net

SEE ALSO

       flow-tools(1)

																     flow-dscan(1)