SILK(7)

NAME
SiLK - the System for Internet-Level Knowledge

DESCRIPTION
SiLK is a collection of traffic analysis tools developed by the CERT Network Situational Awareness Team (CERT NetSA) to facilitate security analysis of large networks. The SiLK tool suite supports the efficient collection, storage, and analysis of network flow data, enabling network security analysts to rapidly query large historical traffic data sets. SiLK is ideally suited for analyzing traffic on the backbone or border of a large, distributed enterprise or mid-sized ISP.

A SiLK installation consists of two categories of applications: the analysis suite and the packing system.

  Analysis suite
The SiLK analysis suite is a collection of command-line tools for processing SiLK Flow records created by the SiLK packing system. These tools read binary files containing SiLK Flow records and partition, sort, and count these records. The most important analysis tool is rwfilter(1), an application for querying the central data repository for SiLK Flow records that satisfy a set of filtering options. The tools are intended to be combined in various ways to perform an analysis task. A typical analysis uses UNIX pipes and intermediate data files to share data between invocations of tools.

The tools, configuration files, and plug-in modules that make up the analysis tools are listed below, roughly grouped by functionality.

Filtering, sorting, and display

rwfilter(1) partitions SiLK Flow records into one or more 'pass' and/or 'fail' output streams. rwfilter is the primary tool for pulling flows from the data store.

silk.conf(5) is the configuration file naming the Classes, Types, and Sensors available at your installation.

rwsort(1) sorts SiLK Flow records using a user-specified key comprised of record attributes, and writes the records to the named output path or to the standard output. Users can define new key fields using plug-ins written in C or PySiLK.

rwcut(1) prints the attributes of SiLK Flow records in a delimited, columnar, human-readable format. Users can define new printable attributes using plug-ins written in C or PySiLK.

SiLK Python Extension

pysilk(3). PySiLK, the SiLK Python extension, allows one to read, manipulate, and write SiLK Flow records, IPsets, and Bags from within Python. PySiLK may be used in a stand-alone Python program or to write plug-ins for several SiLK applications. This document describes the objects, methods, and functions that PySiLK provides. The next entry describes using PySiLK from within a plug-in.

silkpython(3). The SiLK Python plug-in provides a way to use PySiLK to define new partitioning rules for rwfilter(1), new key fields for rwcut(1), rwgroup(1), and rwsort(1), and new key or value fields for rwstats(1) and rwuniq(1).

Counting and statistics

rwuniq(1) bins (groups) SiLK Flow records by a user-specified key comprised of record attributes and prints the total byte, packet, and/or flow counts for each bin. rwuniq can also print distinct source IP and destination IP counts. Users can define new key fields and value fields using plug-ins written in C or PySiLK.

rwcount(1) summarizes SiLK Flow records across time, producing textual output with counts of bytes, packets, and flow records for each time bin.

rwstats(1) summarizes SiLK Flow records by a user-specified key comprised of record attributes, computes values from the flow records that match each key, sorts the results by the value to generate a Top-N or Bottom-N list, and prints the results. Users can define new key fields and value fields using plug-ins written in C or PySiLK.

rwtotal(1) summarizes SiLK Flow records by a specified key and prints the sum of the byte, packet, and flow counts for flows matching the key.

rwaddrcount(1) summarizes SiLK flow records by the source or destination IP and prints the byte, packet, and flow counts for each IP.

IPset, Bag, and Prefix Map manipulation

rwset(1) reads SiLK Flow records and generates binary IPset file(s) containing the source IP addresses or destination IP addresses seen on the flow records.

rwsetbuild(1) reads (textual) IP addresses in dotted-quad or CIDR notation from an input file or from the standard input and writes a binary IPset file.

rwsetcat(1) prints the contents of a binary IPset file as text. Additional information about the IPset file can be printed.

rwsettool(1) performs union, intersection, difference, and sampling functions on the input IPset files, generating a new IPset file.

rwsetmember(1) determines whether the IP address specified on the command line is contained in an IPset.

rwsetintersect(1) generates a new IPset file by performing intersection and difference operations on the IPset files listed on the command line. This command is deprecated; use rwsettool instead.

rwsetunion(1) merges the input binary IPset files into the output IPset; an IP in any input file will be in the output file. This command is deprecated; use rwsettool instead.

rwbag(1) reads SiLK Flow records and builds binary Bag(s) containing key-count pairs. An example is a Bag containing the sum of the byte counts for each source port seen on the flow records.

rwbagbuild(1) creates a binary Bag file from a binary IPset file or from a textual input file.

rwbagcat(1) prints binary Bag files as text.

rwbagtool(1) performs operations (e.g., addition, subtraction) on binary Bag files and produces a new Bag file.

rwpmapbuild(1) reads textual input and creates a binary prefix map file for use with the Address Type (addrtype(3)) and Prefix Map (pmapfilter(3)) Plug-Ins.

rwpmapcat(1) prints information about a prefix map file as text. By default, prints each IP range in the prefix map and its label.

rwipaimport(1) imports a SiLK IPset, Bag, or Prefix Map file into the IP Address Association (IPA <http://tools.netsa.cert.org/ipa/>) library.

rwipaexport(1) exports a set of IP addresses from the IP Address Association (IPA) library to a SiLK IPset, Bag, or Prefix Map.

Run time plug-ins

addrtype(3). The Address Type plug-in provides a way to map an IP address to an integer denoting the IP as internal, external, or non-routable.

ccfilter(3). The Country Code plug-in provides a mapping from an IP address to two-letter, lowercase abbreviation of the country that owns the IP address. The abbreviations used by the Country Code plug-in are those used by the Root-Zone Whois Index (see for example <http://www.iana.org/cctld/cctld-whois.htm>).

flowrate(3). The Flowrate plug-in, which must be loaded explicitly, adds switches and fields to compute packets/second, bytes/second, bytes/packet, payload-bytes, and payload-bytes/second.

pmapfilter(3). The Prefix map plug-in provides a way to map field values to string labels based on a user-defined map file. The map file is created by rwpmapbuild(1).

Record grouping and masking

rwgroup(1) groups SiLK flow records by a user-specified key comprised of record attributes, labels the records with a group ID that is stored in the next-hop IP field, and writes the resulting flows to the specified output path or to the standard output. rwgroup requires that its input is sorted.

rwmatch(1) matches (mates) records as queries and responses and marks mated records with an ID that is stored in the next-hop IP field. rwmatch requires that its input is sorted.

rwnetmask(1) reads SiLK Flow records, zeroes the least significant bits of the source-, destination-, and/or next-hop-IP address(es), and writes the resulting records to the named output path or to the standard output.

Packet and external flow-format processing

rwp2yaf2silk(1) converts a packet capture (pcap(3)) file---such as a file produced by tcpdump(1)---to a single file of SiLK Flow records. rwp2yaf2silk assumes that the yaf(1) (<http://tools.netsa.cert.org/yaf/>) and rwipfix2silk(1) commands are available on your system as it is a simple Perl wrapper around those commands.

rwipfix2silk(1) converts a stream of IPFIX (Internet Protocol Flow Information eXport) records to the SiLK Flow record format.

rwsilk2ipfix(1) converts a stream of SiLK Flow records to an IPFIX (Internet Protocol Flow Information eXport) format.

rwpcut(1) reads a packet capture file and print its contents in a textual form similar to that produced by rwcut.

rwpdedupe(1) detects and eliminates duplicate records from multiple packet capture input files. See also rwdedupe(1).

rwpmatch(1) filters a packet capture file by writing only packets whose five-tuple and timestamp match corresponding records in a SiLK Flow file.

rwptoflow(1) reads a packet capture file and generates a SiLK Flow record for every packet.

Scan detection

rwscan(1) attempts to detect scanning activity from SiLK Flow records. rwscan can produce files that can be loaded into a database and queried with rwscanquery.

rwscanquery(1) queries the scan database which has been populated from database load files generated by rwscan.

Utilities

mapsid(1) maps between sensor names and sensor IDs using the values specified in the silk.conf(5) file.

num2dot(1) reads delimited text from the standard input, converts integer values in the specified column(s) (default first column) to dotted-decimal IP address, and prints the result to the standard output.

rwappend(1) appends the SiLK Flow records contained in the second through final file name arguments to the records contained in the first file name argument.

rwcat(1) reads SiLK Flow records from the files named on the command line, or from the standard input when no files are provided, and writes the SiLK records to the specified output file or to the standard output if it is not connected to a terminal.

rwdedupe(1) reads SiLK Flow records from files named on the command line or from the standard input and writes the records to the named output path or to the standard output, removing any duplicate flow records. Note that rwdedupe will reorder the records as part of its processing.

rwfglob(1) prints to the standard output the list of files that rwfilter would normally process for a given set of file selection switches.

rwcompare(1) determines whether two SiLK Flow files contain the same flow records.

rwfileinfo(1) prints information (type, version, etc.) about a SiLK Flow, IPset, Bag, or Prefix Map file.

rwgeoip2ccmap(1) creates the country code prefix map required by the ccfilter(3) plug-in from the MaxMind GeoIP database.

rwidsquery(1) invokes rwfilter to find flow records matching Snort signatures.

rwip2cc(1) maps a (textual) list of IP addresses to their country code.

rwrandomizeip(1) generates a new SiLK Flow file by substituting a pseudo-random IP address for the source and destination IP addresses in given input file.

rwresolve(1) reads delimited text from the standard input, attempts to resolve the IP addresses in the specified column(s) to host names, and prints the result to the standard output.

rwsplit(1) reads SiLK Flow records and generates a set of sub-files from the input. The sub-files can be limited by flow-, byte-, or packet-counts, or by unique IP count. In addition, the sub-file may contain all the flows or only a sample of them.

rwswapbytes(1) generates a new SiLK Flow file by changing the byte order of the records in a given input SiLK Flow file.

rwtuc(1) generates SiLK flow records from textual input; the input should be in a form similar to what rwcut(1) generates.

silk_config(1) prints information about how SiLK was compiled; this information can be used to compile and link other files and programs against the SiLK header files and libraries.

  Packing system
The SiLK Packing System is comprised of daemon applications that collect flow records (IPFIX flows from yaf(1) or NetFlow v5 or v9 PDUs from a router), convert the records to the SiLK flow format, categorize the flows as incoming or outgoing, and write the records to their final destination in binary flat files for use by the analysis suite. Files are organized in a time-based directory hierarchy with files covering each hour at the leaves.

The tools that make up the SiLK Packing System are:

flowcap(8) listens to flow generators (devices which produce network flow data) and stores the data in temporary files prior to transferring the files to a remote machine for processing by rwflowpack.

rwflowpack(8) reads flow data either directly from a flow generator or from files generated by flowcap, converts the data to the SiLK flow record format, categorizes the flow records, and writes the records either to hourly flat-files organized in a time-based directory structure or to files for transfer to a remote machine for processing by rwflowappend.

rwflowappend(8) watches a directory for files containing small numbers of SiLK flow records and appends those records to hourly files organized in a time-based directory tree.

rwsender(8) watches an incoming directory for files, moves the files into a processing directory, and transfers the files to one or more rwreceiver processes. Either rwsender or rwreceiver may act as the server (i.e., listen for incoming network connections) with the other acting as the client.

rwreceiver(8) accepts files transferred from one or more rwsender processes and stores them in a destination directory. Either rwsender or rwreceiver may act as the server with the other acting as the client.

rwpackchecker(8) reads SiLK Flow records and checks for unusual patterns that may indicate data file corruption.

rwguess(8) reads a file containing NetFlow v5 PDU records and prints the SNMP interfaces that are used most often and the number of records seen for each interface.

sensor.conf(5) is a configuration file for sensors and probes used by rwflowpack and flowcap.

ENVIRONMENT
The following environment variables affect the tools in the SiLK tool suite.

SILK_CONFIG_FILE
    This environment variable contains the location of the site configuration file, silk.conf(5). This variable has precedence over all methods of finding the site file except for the --site-config-file switch on the applications.

SILK_DATA_ROOTDIR
    This variable gives the root of directory tree where the data store of SiLK Flow files is maintained, overriding the location that is compiled into the tools. The rwfilter(1) and rwfglob(1) tools use this value when selecting which flow files to process unless the user passes the --data-rootdir switch to the application. In addition, the SiLK tools will search for the site configuration file, silk.conf, in this directory.

SILK_PATH
    This environment variable gives the root of the directory tree where the tools are installed. As part of its search for the SiLK site configuration file, the SiLK applications check for a file named silk.conf in the directories $SILK_PATH/share/silk and $SILK_PATH/share. These directories are also searched when any other configuration file is required (e.g., the country code map required by ccfilter(3)). In addition, the applications that support plug-ins will search for them in $SILK_PATH/lib/silk, $SILK_PATH/share/lib and $SILK_PATH/lib.

SILK_IPV6_POLICY
    For tools that implement the --ipv6-policy switch, this environment variable is used as the value for that switch when it is not provided.

SILK_PAGER
    When set to a non-empty string, most of the applications that produce textual output (e.g., rwcut(1)) will automatically invoke this program to display their output a screen at a time. If set to an empty string, no paging of the output is performed. The --pager switch on the application overrides this value.

PAGER
    The applications that support paging their output will use the value in this environment variable when SILK_PAGER is not set.

SILK_TMPDIR
    This variable is used by tools that write temporary files (e.g., rwsort(1)) as the directory in which to store those files. SILK_TMPDIR overrides the value of TMPDIR.

TMPDIR
    When set and SILK_TMPDIR is not set, temporary files are created in this directory.

PYTHONPATH
    The Python modules and library files required to use PySiLK from rwfilter(1), rwcut(1), rwsort(1), and rwuniq(1) as well as from Python itself are installed under SiLK's installation tree by default. It may be necessary to set or modify the PYTHONPATH environment variable so Python can find these files. For information on using the PySiLK module, see silkpython(3) as well as the SiLK in Python handbook.

SILK_PYTHON_TRACEBACK
    When set, Python plug-ins will output traceback information on Python errors to the standard error.

SILK_RWFILTER_THREADS
    The number of threads rwfilter uses while reading input files or files selected from the data store.

SILK_COUNTRY_CODES
    This environment variable allows the user to specify the country code mapping file that rwfilter, rwip2cc(1), pysilk(3), and the ccfilter(3) plug-in use. The value may be a complete path or a file relative to SILK_PATH. If the variable is not specified, the code looks for a file named country_codes.pmap in the location specified by SILK_PATH.

RWRECEIVER_TLS_PASSWORD, RWSENDER_TLS_PASSWORD
    Used by rwreceiver(8) and rwsender(8), this variable specifies the password to use to decrypt the PKCS#12 file specified in the --tls-pkcs12 switch.

SILK_LOGSTATS_RWFILTER
    When set to a non-empty value, rwfilter(1) will treat the value as the path to a program to execute with information about this rwfilter invocation. Its purpose is to provide the SiLK administrator with information on how the SiLK tool set is being used.

SILK_LOGSTATS
    This environment variable is currently an alias for SILK_LOGSTATS_RWFILTER. The ability to log invocations may be extended to other SiLK tools in future releases.

SILK_LOGSTATS_DEBUG
    If the environment variable is set to a non-empty value, rwfilter will print messages to the standard error about the SILK_LOGSTATS value being used and either the reason why the value cannot be used or the arguments to the external program being executed.

SILK_PLUGIN_DEBUG
    When set to a non-empty value, an application that supports plug-ins will print status messages to the standard error as it tries to open each of its plug-ins.

SEE ALSO
Analysts' Handbook: Using SiLK for Network Traffic Analysis, The SiLK Reference Guide, SiLK Installation Handbook, <http://tools.netsa.cert.org/silk/>