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.

SiLK consists of two sets of tools: a packing system and analysis
suite. The packing system receives network flow information from
Netflow v5 or any IPFIX-based flowmeter and converts them into a more
space efficient format, recording the packed records into
service-specific, binary flat files. The analysis suite consists of
tools which can read these flat files and then 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.