SiLK, the System for Internet-Level Knowledge, 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 packing system and the analysis suite. The packing system collects IPFIX, NetFlow v9, or NetFlow v5 and converts the data into a more space efficient format, recording the packed records into service-specific binary flat files. The analysis suite consists of tools which read these flat files and perform various query operations, ranging from per-record filtering to statistical analysis of groups of records. The analysis tools interoperate using pipes, allowing a user to develop a relatively sophisticated query from a simple beginning.

The vast majority of the current code-base is implemented in C, Perl, or Python. This code has been tested on Linux, Solaris, OpenBSD, Mac OS X, and Cygwin, but should be usable with little or no change on other Unix platforms.

The SiLK software components are released under the GNU Public License V2.