This is a modified version of nfdump utilities to support the Sagan log analysis engine (http://sagan.quadrantsec.com).

When compiling, build with the "--enable-sagan" flag. This adds a new command line option for nfcapd (-F). For example:

nfcapd -l /var/log/netflow-archive -p 2056 -F /var/run/sagan-netflow.fifo

This tells nfcapd to record data, as normal, to the /var/log/netflow-archive directory. "nfcapd" will listen on UDP port 2056 for NetFlow data. The decoded data will also be written to the /var/run/sagan-netflow.fifo. The modified nfcapd will dump the NetFlow data in a Sagan/FIFO format. That is to say, no additional formating is necessary.

More information can be found at:

https://wiki.quadrantsec.com/twiki/bin/view/Main/SaganNetflow

Stable Release v1.6.10

See the Changelog file for all changes in release 1.6.10

nfdump-1.6.9 includes a new written from scratch implemented NSEL/ASA module. It's based on the CISCO ASA Spec 8.4: "Implementation Note for NetFlow Collectors, Version 8.4" Due to this new implementation, nfdump-1.6.9 is not compatible with old nfdump-1.5.8-2-NSEL. To build nfdump, add --enable-nsel to the configure command. By enabling the ASA/NSEL option, nfdump processes normal flows as well ASA/NSEL records likewise. nfcapd adds by default all required NSEL extesions equivalent to '-Tnsel'

nfdump-1.6.9 includes a new module for decoding the CISCO NEL ( NAT event logging ) records. It's considered to be experimantal, as no official documentation can be found. Let me know otherwise. To build nfdump, add --enable-nel to the configure command. By enabling the NEL option, nfdump processes normal flows as well NEL records likewise. nfcapd adds by default all required NEL extesions equivalent to '-Tnel'

Although it's possibel to enable NSEL und NEL likewise, users could get confused by nfdump output, as NSEL output format overwrites NEL format. In that case you need explicitly to define -o nel.

nfdump contains an IPFIX module for decoding IPFIX data. It is considered not yet to be complete and does not yet support full IPFIX. o Supports basically same feature set of elements as netflow_v9 module o Only UDP traffic is accepted no SCTP so far o No sampling support. o Still more test data needed. If you would like to see more IPFIX support, please contact me.

This is a small description, what the nfdump tools do and how they work. Nfdump is distributed under the BSD license - see BSD-license.txt

The nfdump tools collect and process netflow data on the command line. They are part of the NFSEN project, which is explained more detailed at http://www.terena.nl/tech/task-forces/tf-csirt/meeting12/nfsen-Haag.pdf

The Web interface mentioned is not part of nfdump and is available at http://nfsen.sourceforge.net

nfcapd - netflow collector daemon. Reads the netflow data from the network and stores the flow records into files. Automatically rotates files every n minutes. ( typically every 5 min ) nfcapd reads netflow versions v1, v5, v7 and v9 flows as well as IPFIX flows transparently. Several netflow streams can be sent to a single or collector.

nfdump - netflow dump. Reads the netflow data from the files stored by nfcapd. It's filter syntax is similar to tcpdump ( pcap like ) but for netflow adapted. If you like tcpdump you will like nfdump. nfdump displays netflow data and/or creates top N statistics of flows, bytes, packets. nfdump has a powerful and flexible flow aggregation including bi-directional flows. The output format is user selectable and also includes a simple csv format for post processing.

nfreplay - netflow replay Reads the netflow data from the files stored by nfcapd and sends it over the network to another host.

nfexpire - expire old netflow data Manages data expiration. Sets appropriate limits.

Optional binaries:

nfprofile - netflow profiler. Required by NfSen Reads the netflow data from the files stored by nfcapd. Filters the netflow data according to the specified filter sets ( profiles ) and stores the filtered data into files for later use.

nftrack - Port tracking decoder for NfSen plugin PortTracker.

ft2nfdump - read flow-tools format - Optional tool ft2nfdump acts as a pipe converter for flow-tools data. It allows to read any flow-tools data and process and save it in nfdump format.

sfcapd - sflow collector daemon scfapd collects sflow data and stores it into nfcapd comaptible files. "sfcapd includes sFlow(TM), freely available from http://www.inmon.com/".

nfreader - Framework for programmers nfreader is a framework to read nfdump files for any other purpose. Own C code can be added to process flows. nfreader is not installed

parse_csv.pl - Simple reader, written in Perl. parse_csv.pl reads nfdump csv output and print the flows to stdout. This program is intended to be a framework for post processing flows for any other purpose.

Note for sflow users: sfcapd and nfcapd can be used concurrently to collect netflow and sflow data at the same time. Generic command line options apply to both collectors likewise. Due to lack of availability of sflow devices, I could not test the correct output of IPv6 records. Users are requested to send feedback to the list or directly to me. sfcapd's sflow decoding module is based on InMon's sflowtool code and supports similar fields as nfcapd does for netflow v9, which is a subset of all available sflow fields in an sflow record. More fields may be integrated in future versions of sfcapd.

Binary data files can optionally be compressed using the fast LZO1X-1 compression. For more details on this algorithm see, http://www.oberhumer.com/opensource/lzo. LZO1X-1 is very fast, so that compression can be used in real time by the collector. LZO1X-1 reduces the file size around 50%. You can check the compression speed for your system by doing ./nftest <path/to/an/existing/netflow/file>.

The goal of the design is to able to analyze netflow data from the past as well as to track interesting traffic patterns continuously. The amount of time back in the past is limited only by the disk storage available for all the netflow data. The tools are optimized for speed for efficient filtering. The filter rules should look familiar to the syntax of tcpdump ( pcap compatible ).

All data is stored to disk, before it gets analyzed. This separates the process of storing and analyzing the data.

The data is organized in a time-based fashion. Every n minutes

• typically 5 min - nfcapd rotates and renames the output file with the timestamp nfcapd.YYYYMMddhhmm of the interval e.g. nfcapd.200907110845 contains data from July 11th 2009 08:45 onward. Based on a 5min time interval, this results in 288 files per day.

Analyzing the data can be done for a single file, or by concatenating several files for a single output. The output is either ASCII text or binary data, when saved into a file, ready to be processed again with the same tools.

You may have several netflow sources - let's say 'router1' 'router2' and so on. The data is organized as follows:

/flow_base_dir/router1 /flow_base_dir/router2

which means router1 and router2 are subdirs of the flow_base_dir.

Although several flow sources can be sent to a single collector, It's recommended to have multiple collector on busy networks for each source. Example: Start two collectors on different ports:

nfcapd -w -D -S 2 -B 1024000 -l /flow_base_dir/router1 -p 23456 nfcapd -w -D -S 2 -B 1024000 -l /flow_base_dir/router2 -p 23457

nfcapd can handle multiple flow sources. All sources can go into a single file or can be split:

All into the same file: nfcapd -w -D -S 2 -l /flow_base_dir/routers -p 23456

Collected on one port and split per source: nfcapd -w -D -S 2 -n router1,172.16.17.18,/flow_base_dir/router1
-n router2,172.16.17.20,/flow_base_dir/router2 -p 23456

See nfcapd(1) for a detailed explanation of all options.

Security: none of the tools requires root privileges, unless you have a port < 1024. However, there is no access control mechanism in nfcapd. It is assumed, that host level security is in place to filter the proper IP addresses.

See the manual pages or use the -h switch for details on using each of the programs. For any questions send email to phaag@users.sourceforge.net

Configure your router to export netflow. See the relevant documentation for your model.

A generic Cisco sample configuration enabling NetFlow on an interface:

ip address 192.168.92.162 255.255.255.224
 interface fastethernet 0/0
 ip route-cache flow

To tell the router where to send the NetFlow data, enter the following global configuration command:

ip flow-export 192.168.92.218 9995
ip flow-export version 5 

ip flow-cache timeout active 5

This breaks up long-lived flows into 5-minute segments. You can choose any number of minutes between 1 and 60;

Netflow v9 full export example of a cisco 7200 with sampling enabled:

interface Ethernet1/0
 ip address 192.168.92.162 255.255.255.224
 duplex half
 flow-sampler my-map
!
!
flow-sampler-map my-map
 mode random one-out-of 5
!
ip flow-cache timeout inactive 60
ip flow-cache timeout active 1
ip flow-capture fragment-offset
ip flow-capture packet-length
ip flow-capture ttl
ip flow-capture vlan-id
ip flow-capture icmp
ip flow-capture ip-id
ip flow-capture mac-addresses
ip flow-export version 9
ip flow-export template options export-stats
ip flow-export template options sampler
ip flow-export template options timeout-rate 1
ip flow-export template timeout-rate 1
ip flow-export destination 192.168.92.218 9995

See the relevant documentation for a full description of netflow commands

Note: Netflow version v5 and v7 have 32 bit counter values. The number of packets or bytes may overflow this value, within the flow-cache timeout on very busy routers. To prevent overflow, you may consider to reduce the flow-cache timeout to lower values. All nfdump tools use 64 bit counters internally, which means, all aggregated values are correctly reported.

The binary format of the data files is netflow version independent. For speed reasons the binary format is machine architecture dependent, and as such can not be exchanged between little and big endian systems. Internally nfdump does all processing IP protocol independent, which means everything works for IPv4 as well as IPv6 addresses. See the nfdump(1) man page for details.

netflow version 9: nfcapd supports a large range of netflow v9 tags. Version 1.6 nfdump supports the following fields. This list can be found in netflow_v9.h

// Flowset record types #define NF9_IN_BYTES 1 #define NF9_IN_PACKETS 2 #define NF9_FLOWS_AGGR 3 #define NF9_IN_PROTOCOL 4 #define NF9_SRC_TOS 5 #define NF9_TCP_FLAGS 6 #define NF9_L4_SRC_PORT 7 #define NF9_IPV4_SRC_ADDR 8 #define NF9_SRC_MASK 9 #define NF9_INPUT_SNMP 10 #define NF9_L4_DST_PORT 11 #define NF9_IPV4_DST_ADDR 12 #define NF9_DST_MASK 13 #define NF9_OUTPUT_SNMP 14 #define NF9_V4_NEXT_HOP 15 #define NF9_SRC_AS 16 #define NF9_DST_AS 17 #define NF9_BGP_V4_NEXT_HOP 18

#define NF9_LAST_SWITCHED 21 #define NF9_FIRST_SWITCHED 22 #define NF9_OUT_BYTES 23 #define NF9_OUT_PKTS 24

#define NF9_IPV6_SRC_ADDR 27 #define NF9_IPV6_DST_ADDR 28 #define NF9_IPV6_SRC_MASK 29 #define NF9_IPV6_DST_MASK 30

#define NF9_IPV6_FLOW_LABEL 31 #define NF9_ICMP_TYPE 32

#define NF9_SAMPLING_INTERVAL 34 #define NF9_SAMPLING_ALGORITHM 35

#define NF9_ENGINE_TYPE 38 #define NF9_ENGINE_ID 39

#define NF9_FLOW_SAMPLER_ID 48 #define FLOW_SAMPLER_MODE 49 #define NF9_FLOW_SAMPLER_RANDOM_INTERVAL 50

// #define NF9_MIN_TTL 52 // #define NF9_MAX_TTL 53 // #define NF9_IPV4_IDENT 54

#define NF9_DST_TOS 55 #define NF9_IN_SRC_MAC 56 #define NF9_OUT_DST_MAC 57 #define NF9_SRC_VLAN 58 #define NF9_DST_VLAN 59

#define NF9_DIRECTION 61 #define NF9_V6_NEXT_HOP 62 #define NF9_BPG_V6_NEXT_HOP 63 // #define NF9_V6_OPTION_HEADERS 64

#define NF9_MPLS_LABEL_1 70 #define NF9_MPLS_LABEL_2 71 #define NF9_MPLS_LABEL_3 72 #define NF9_MPLS_LABEL_4 73 #define NF9_MPLS_LABEL_5 74 #define NF9_MPLS_LABEL_6 75 #define NF9_MPLS_LABEL_7 76 #define NF9_MPLS_LABEL_8 77 #define NF9_MPLS_LABEL_9 78 #define NF9_MPLS_LABEL_10 79 #define NF9_IN_DST_MAC 80 #define NF9_OUT_SRC_MAC 81

#define NF9_FORWARDING_STATUS 89

#define NF9_BGP_ADJ_NEXT_AS 128 #define NF9_BGP_ADJ_PREV_AS 129

// CISCO ASA NSEL extension - Network Security Event Logging #define NF_F_FLOW_BYTES 85 #define NF_F_CONN_ID 148 #define NF_F_FLOW_CREATE_TIME_MSEC 152 #define NF_F_ICMP_TYPE 176 #define NF_F_ICMP_CODE 177 #define NF_F_ICMP_TYPE_IPV6 178 #define NF_F_ICMP_CODE_IPV6 179 #define NF_F_FWD_FLOW_DELTA_BYTES 231 #define NF_F_REV_FLOW_DELTA_BYTES 232 #define NF_F_FW_EVENT84 233 #define NF_F_EVENT_TIME_MSEC 323 #define NF_F_INGRESS_ACL_ID 33000 #define NF_F_EGRESS_ACL_ID 33001 #define NF_F_FW_EXT_EVENT 33002 #define NF_F_USERNAME 40000 #define NF_F_XLATE_SRC_ADDR_IPV4 40001 #define NF_F_XLATE_DST_ADDR_IPV4 40002 #define NF_F_XLATE_SRC_PORT 40003 #define NF_F_XLATE_DST_PORT 40004 #define NF_F_FW_EVENT 40005

// Cisco ASR 1000 series NEL extension - Nat Event Logging #define NF_N_NAT_EVENT 230 #define NF_N_INGRESS_VRFID 234 #define NF_N_NAT_INSIDE_GLOBAL_IPV4 225 #define NF_N_NAT_OUTSIDE_GLOBAL_IPV4 226 #define NF_N_POST_NAPT_SRC_PORT 227 #define NF_N_POST_NAPT_DST_PORT 228

// nprobe latency extensions #define NF9_NPROBE_CLIENT_NW_DELAY_SEC 57554 #define NF9_NPROBE_CLIENT_NW_DELAY_USEC 57555 #define NF9_NPROBE_SERVER_NW_DELAY_SEC 57556 #define NF9_NPROBE_SERVER_NW_DELAY_USEC 57557 #define NF9_NPROBE_APPL_LATENCY_SEC 57558 #define NF9_NPROBE_APPL_LATENCY_USEC 57559

32 and 64 bit counters are supported for any counters. However, internally nfdump stores packets and bytes counters always as 64bit counters. 16 and 32 bit AS numbers are supported.

Extensions: nfcapd supports a large number of v9 tags. In order to optimise disk space and performance, v9 tags are grouped into a number of extensions which may or may not be stored into the data file. Therefore the v9 templates configured on the exporter may be tuned with the collector. Only the tags common to both are stored into the data files. Extensions can be switch on/off by using the -T option.

Sampling: By default, the sampling rate is set to 1 (unsampled) or to any given value specified by the -s cmd line option. If sampling information is found in the netflow stream, it overwrites the default value. Sampling is automatically recognised when announced in v9 option templates (tags #48, #49, #50 ) or in the unofficial v5 header hack. Note: Not all platforms (or IOS versions) support exporting sampling information in netflow data, even if sampling is configured. The number of bytes/packets in each netflow record is automatically multiplied by the sampling rate. The total number of flows is not changed as this is not accurate enough. (Small flows versus large flows)

nfcapd can listen on IPv6 or IPv4. Furthermore multicast is supported.

When building with configure option --enable-ftconv, the flow-tools converter is compiled. Using this converter, any flow-tools created data can be read and processed and stored by nfdump.

Example:

flow-cat [options] | ft2nfdump | nfdump [options]

See the INSTALL file for installation details.