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nfdump-1.7.x or nfdumpunicorn is the current release of nfdump.

nfdump is a toolset in order to collect and process netflow/ipfix and sflow data, sent from netflow/sflow compatible devices.

The toolset contains several collectors to collect flow data:

• nfcapd supports netflowv1,v5/v7,v9 andIPFIX
• sfcapd supportssflow.
• nfpcapd converts pcap data read from a host interface or from pcap files.

The collected flow data is stored into files and can be process afterwards.nfdump processes and lists the flows in many different output formats andcan create a wide range of statistics.

nfdump has a very powerful flow filter to process flows. The filter syn‐tax is very similar to tcpdump, but adapted and extended for flow filter‐ing. A flow filter may also contain arrays ofmany thousand IP addressesetc. to search for specific records.

nfdump can aggreagte flows according to a user defined number of ele‐ments. This masks certain elements and allows to sum up flow recordsmatching the same values.

The combination of flowfiltering andaggregation as input for any flowstatistics allowscomplex flow processing. Pre‐filtered and aggregatedflow data may also be written back into a binary flow file, which againmay be processed with nfdump

nfdump can enrich the listing of flows withgeo location information,AS information andTOR exit node information. AS information is enriched only,if it is not available in the original flow record. IP addresses can be tagged with atwo lettercountry code, or with a longer location label containing the geographicregion, country and city. The geo location and AS information is retrieved from theoptionalgeoDB database, created by thegeolookup program from the nfdumptools. geolookup uses theMaxmind database GeoDB or GeoLite2 to create abinary lookup database for nfdump. Please check the geolooup(1) man pagefor more details. IP adresses can be tagged asTOR exit nodes, from the optionaltorDB database, created by thetorlookup program. Please chaeck the torlookup(1)man page for details.

There is also ago-nfdump module to read nfdump flows files in Golang.

nfdump-1.7.x is compatible to nfdump-1.6.18, which means it can read filescreated with nfdump-1.6.18 or newer. Flow files created with earlier nfdumpversions may not contain all flow elements. If you have older files, it isrecommended to use nfdump-1.6.17 to update the records.

If you have lots of flows files from nfdump-1.6.x, it is recommended to convertthese to the new format. You can convert any old files from nfdump-1.6.x to nfdump-1.7format by reading/writing files:./nfdump -r old-flowfile -y -w new-flowfile

Please note, that onlynfdump may read nfdump-1.6.x flow files. All other programs understandthe new file format only.

Note for NfSen users: If you use NfSen, you must upgrade NfSen to the latest Github versionhttps://github.com/phaag/nfsen.All specific binaries such as nfprofile and nftrack are still available with nfdump-1.7 but may be removed in future.

• nfdump is now a multi-threaded program and uses parallel threads mainly forreading, writing and processing flows as well as for sorting. This may resultin faster flow processing, depending on the tasks. The speedimprovementalso heavily depends on the hardware (SSD/HD) and flow compressionoption.

• For netflow v9 and IPFIX, nfdump now supportsFNF and flexible length fields. Thisimproves compatibility with some exporters such as yaf and others.

• Support for Cisco Network Based Application Recognition (NBAR).

• Supports Maxmind geo location information to tag/geolocate IP addressesand AS numbers.

• Supports TOR exit node information to IP addresses as TOR exit nodes.

• nfpcapd automatically uses TPACKET_V3 for Linux or direct BPF sockets for*BSD. This improves packet processing. It adds new options to collect MAC andVLAN information if requested as well as the payload of the first packet. Thiscreates a lot of new possibilities in order to process and filter flows, suchasnfdump -r flowfile 'payload content "POST"'nfpcapd can now store flow files locally or can sent them to a remote nfcapdcollector.

• Metric exports: By default, every 60s a flow summary statistics can be sentto a UNIX socket. The corresponding program may benfinflux to insertthese metrics into an influxDB ornfexporter for Prometheus monitoring.

• nfdump supports a default config file tipically/usr/local/etc/nfdump.conf tostore user defined paths for thegeolookup andtorlookup database files as well as foruser defined named output formats( -o 'fmt:%ts .. ', -o 'csv:%ts ..'). See the default/usr/local/etc/nfdump.conf.dist file for an example.

The nfdump program suite also containsgeolookup. It allows eitherto enrich IP addresses by country codes/locations and may add potentialmissing AS information. Flows may be filtered according to country codes.( ex:src geo US ). geolookup may also be used as standalone program to lookupIPs for AS/Geo information, similar to the famous Team Cymru whois service.geolookup uses a local database, which allows to process as many requests as you have.In order to use geolookup, you need either a free or paid Maxmind accountin order to convert the Maxmind .csv files into an nfdump vector data file.geolookup needs to be enabled when running configure:--enable-maxmind

The nfdump program suite also containstorlookup. It allows eitherto enrich IP addresses by a TOR exit flag. Flows may be filtered according toTOR IP addresses( ex:src ip tor ). torlookup may also be used as standalone programto lookup IPs for TOR exit node intervals with as many requests as you have.In order to use torlookup or the nfdump output enrichment , you need to create thetordb first. See also the toorlookup(1) man page.torlookup needs to be enabled whenrunning configure:--enable-tor

NSEL (Network Event Security Logging) as well as NEL (NAT Event Logging) are technologies invented byCISCO and also use the netflow v9 protocol. However, NSEL and NEL are not flows as commonly known but ratherEvents! exported from specific devices such as CISCO ASA. nfdump supports Event looging as part of netflow v9.

Jun OS NAT Event Logging is mostly compatible with CISCO's NAT Event Logging - mostly - it needs another data interpretation.See--enable-jnat below

The toolset is build upon the autotools framework. Run./autogen.sh first.Afterwards./configuremake andmake install should do the trick.

For various older Linuxes need a more modern compiler:

%yuminstallcentos-release-scl

Then you can install GCC 8 and its C++ compiler:

%yuminstalldevtoolset-8-gccdevtoolset-8-gcc-c++

To switch to a shell which defaultsgcc andg++ to this GCC version, use:

%sclenabledevtoolset-8--bash

%sudoapt-getinstallclang-10%CC=clang-10 ./configure ...

The following config options are available: ( see ./configure --help for the complete list)

• --enable-sflow
  Build sflow collector sfcapd; default isNO
• --enable-nfpcapd
  Build nfpcapd collector to create netflow data from interface traffic or precollected pcap traffic; default isNO
• --enable-maxmind
  Build geolookup program; default isNO
• --enable-tor
  Build torlookup program; default isNO
• --enable-nsel
  This switch is no longer needed for nfdump-1.7.x, asnsel support is builtin by default. This switch only affectsthe default output format fromline tonsel and has no other effects otherwise; default isNO
• --enable-jnat
  Compile nfdump, to read and process JunOS NAT event loggingNO
• --with-zstdpath=PATHExpect libzstd installed inPATH; default/usr/local
• --enable-ftconv
  Build the flow-tools to nfdump converter; default isNO
• --enable-nfprofile
  Build nfprofile used by NfSen; default isNO
• --enable-nftrack
  Build nftrack used by PortTracker; default isNO
• --enable-ja4Enable all ja4 module; default isNOSee JA4-FingerprintingJA4 Fingerprinting module.

Development and beta options

• --enable-devel
  Insert lots of debug and development code into nfdump for testing and debugging; default isNO
• --enable-readpcap
  Add code to nfcapd to read flow data also from pcap files; default isNO

nfcapd - netflow collector daemon.
Collects the netflow data, sent from exporters and stores the flow recordsinto files. Automatically rotates files every n minutes. ( typicallyevery 5 min ) The netflow versions mentioned above are read transparentlyMultiple netflow streams can be collected by a single or collector.
nfcapd can listen on IPv6 or IPv4. Furthermore multicast is supported.

nfdump - process collected netflow records.
Nfdump reads the netflow data from one or many files stored by nfcapd.It's filter syntax is similar to tcpdump ( pcap like ) but adapted for netflow.If you like tcpdump you will like nfdump. nfdump displays netflowdata and/or creates top N statistics of flows, bytes, packets. nfdumphas a powerful and flexible flow aggregation including bi-directionalflows. The output format is user selectable and also includes a simplecsv format for post processing.

nfanon - anonymize netflow records
IP addresses in flow records are anonimized using the CryptoPAn method.

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

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

sfcapd - sflow collector daemon
scfapd collects sflow data and stores it into nfcapd compatible files."sfcapd includes sFlow(TM) code, freely available fromhttps://github.com/sflow/sflowtool.

nfpcapd - pcap to netflow collector daemon
nfpcapd listens on a network interface, or reads precollected pcap traffic.It either stores locally flow records into nfcapd compatible files or sendsthe flows to a remotenfcapd collector. It is nfcapd's companion to converttraffic directly into nfdump records. Nfpcap can optionally integrate lots ofmeta data as well as prt of the payload. (-o fat, payload)

geolookup - Geo location lookup program.geolookup converts Maxmind's .csv files into the nfdump vector DB. Theconverted DB may be used as a standalone lookup tool, or be be used bynfdump in order to automatically lookup country and location.Please note: You need a legitimate Maxmind account (free or paid) inorder to download the files.

torlookup - TOR location lookup program.torlookup converts tor information files into the nfdump vector DB. Theconverted DB may be used as a standalone lookup tool, or be be used bynfdump in order to automatically flag tor exit node IPs.

ft2nfdump - flow-tools flow converter
ft2nfdump converts flow-tools data into nfdump format.

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

nftrack - Port tracking decoder for NfSen plugin PortTracker.

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

sfcapd and nfcapd can be used concurrently to collect netflow and sflowdata at the same time. Generic command line options apply to bothcollectors likewise. sfcapd's sflow decoding module is based on InMon'ssflowtool 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 by using either LZO1X-1, LZ4, ZSTD or bzip2 compressionLZO is fastest but less efficient, LZ4 and ZSTD are fast and pretty efficient and bzip2 is slow but efficient.

By default LZO and LZ4 embedded without external dependancies. Bzip2 and ZSTD are optional libraries, which are automatically added, if they are found while configuring and compiling.

The standardconfigure process checks for the installed libraries lz4, bz2 and zstd and enables them if they are found.configure understands the following options:

  --with-lz4path=PATH     Expect liblz4 installed in PATH; default /usr/local  --with-zstdpath=PATH    Expect libzstd installed in PATH; default /usr/local  --with-bz2path=PATH     Expect libbz2 installed in PATH; default /usr/local

If no option is given and no library is found that compression algorithm is disabled. For LZ4, if no library is found, the embedded version is used. Compression algorithms can also be explicitly disabled by settingwith-xxxpath=no In the case of lz4, it disables the system installed version and uses the embedded one.

Recommendation

If you compress automatically flows while they are collected, use LZ4-z=lz4 as a standard.

Notes: Bzip2 uses about 30 times more CPU than LZO1X-1. Use bzip2 to archive netflowdata, which may reduce the disk usage again by a factor of 2. The compression of flow filescan be changed any time with nfdump -J <algo[:level]>. You may also apply compression levels to lz4 and zstd such as-z=zstd:9 or-z=lz4:5 to improve efficiency at the cose of more CPU and slower compression speed.

For more details on each methde, see:

LZO1X-1:http://www.oberhumer.com/opensource/lzo

LZ4:https://github.com/lz4/lz4

ZSTD:https://github.com/facebook/zstd

bzip2:http://www.bzip.org

The goal of the design is to able to analyze netflow data fromthe past as well as to track interesting traffic patternscontinuously. The amount of time back in the past is limited onlyby the disk storage available for all the netflow data. The toolsare optimized for speed for efficient filtering. The filter rulesshould look familiar to the syntax of tcpdump ( pcap compatible ).

All data is stored to disk, before it gets analyzed. This separatesthe 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 filewith 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 concatenatingseveral files for a single output. The output is either ASCII textor binary data, when saved into a file, ready to be processed againwith 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 foreach source.Example: Start two collectors on different ports:

nfcapd -D -S 2 -B 1024000 -w /flow_base_dir/router1 -p 23456nfcapd -D -S 2 -B 1024000 -w /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 -D -S 2 -w /flow_base_dir/routers -p 23456

Collected on one port and split per source:

nfcapd -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 havea port < 1024. However, there is no access control mechanism in nfcapd.It is assumed, that host level security is in place to filter theproper IP addresses.

See the manual pages or use the -h switch for details on using each ofthe programs. For any questions send email topeter@people.ops-trust.net

Configure your router to export netflow. See the relevant documentationfor 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 followingglobal configuration command:

ip flow-export 192.168.92.218 9995ip flow-export version 5 ip flow-cache timeout active 5

This breaks up long-lived flows into 5-minute segments. You can chooseany 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 60ip flow-cache timeout active 1ip flow-capture fragment-offsetip flow-capture packet-lengthip flow-capture ttlip flow-capture vlan-idip flow-capture icmpip flow-capture ip-idip flow-capture mac-addressesip flow-export version 9ip flow-export template options export-statsip flow-export template options samplerip flow-export template options timeout-rate 1ip flow-export template timeout-rate 1ip 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 ofpackets or bytes may overflow this value, within the flow-cache timeouton very busy routers. To prevent overflow, you may consider to reduce theflow-cache timeout to lower values. All nfdump tools use 64 bit countersinternally, 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, andas such can not be exchanged between little and big endian systems.Internally nfdump does all processing IP protocol independent, which meanseverything works for IPv4 as well as IPv6 addresses.See the nfdump(1) man page for details.

netflow version 9 and infix:nfcapd supports a large range of netflow v9 and ipfix tags. Version 1.7 of nfdumpalso supports FNF - flexible netflow, subtemplates and understands a few specific exporters such asyaf.

This collector collects sflowhttps://www.sflow.org exports. It is largely identical to nfcapd except it only understands sflow packets.

This collector is able to listen on a host interface and generates netflow data from the network data stream on that interface. It make use ofPACKET_RX_RING to read packets on an interface device level (TPACKETV3) on Linux hosts or of theBPF interface - Berkeley Packet Filter on *BSD hosts which provides raw access to data link layers. Nfpcapd builds an internal netflow cache which is periodically written to disk or forwarded to an nfcapd server. As a special feature, nfpcpad may collect the first few bytes of a network connection, if requested to do so (-o payload), which allows filter and evaluate the flows with nfdump later.

Listen on eth0 and store the flows locally. Set flow cache active timeout to 60s, inactive tiemout to 30s:

nfpcapd -D -S 2 -w /var/flows -i eth0 -e 60,30 -u daemon -g daemon

Listen on eth0 and forward flow data to nfcapd running on a remote host. Add tunnel infos, MAC addr, vlan labels and first packet payload to the flows:

nfpcapd -D -S 2 -H 192.168.168.40 -i eth0 -e 60,30 -o fat,payload -u daemon -g daemon

In order to evaluate the payload, nfdump has some simple payload decoders for DNS, ja3, ja3s, ja4 and a few other.

Alternatively nfpcapd can also convert existing cap files into flow data:

nfpcapd -S 2 -w /var/flows -r pcapfile.pcap -e 60,30 -o fat,payload

Links

Extensions: nfcapd supports a large number of v9 tags. It automatically addextensions to store data for v9/IPFIX elements which are supported.

By default, the sampling rate is set to 1 (unsampled) or to any given value specifiedby the-s cmd line option. If sampling information is found in the netflow stream,it overwrites the default value. Sampling is automatically recognised when announcedin v9/ipfix option templates with tags set (#302, #304, #305, #306), (#48, #49, #50 ), (#34, #35)or in the unofficial v5 header hack. The sampling data is stored in the samplingPacketInterval/PacketSpace model. If announced differently, it is converted accordingly.

Note: Not all platforms (or vendor software versions) support exporting sampling informationin netflow data, even if sampling is configured. The number of bytes/packets in eachnetflow record is automatically multiplied by the sampling rate. The total number offlows is not changed as this is not accurate enough. (Small flows versus large flows)

If you like this project your company may consider sponsoring it :)https://github.com/sponsors/phaag