Monitoring software may use libpcap, WinPcap, or Npcap to capture network packets traveling over a computer network and, in newer versions, to transmit packets on a network at the link layer, and to get a list of network interfaces for possible use with libpcap, WinPcap, or Npcap.
The pcap API is written in C, so other languages such as Java, .NET languages, and scripting languages generally use a wrapper; no such wrappers are provided by libpcap or WinPcap itself. C++ programs may link directly to the C API or make use of an object-oriented wrapper.
Most current Unix-like systems provide a mechanism by which a program can capture network traffic to and from the machine running the program and, in some cases, other traffic to which that machine is attached. However, these mechanisms are significantly different from one another; the libpcap library provides a common API to access these mechanisms, allowing programs to be written to capture network traffic without having to worry about the details of all those mechanisms.
libpcap, WinPcap, and Npcap also support saving captured packets to a file, and reading files containing saved packets; applications can be written, using libpcap, WinPcap, or Npcap, to be able to capture network traffic and analyze it, or to read a saved capture and analyze it, using the same analysis code. A capture file saved in the format that libpcap, WinPcap, and Npcap use can be read by applications that understand that format, such as tcpdump, Wireshark, CA NetMaster, or Microsoft Network Monitor 3.x. The file format is described by Internet-Draft draft-ietf-opsawg-pcap;[5] the current editors' version of the draft is also available.[6]
The MIME type for the file format created and read by libpcap, WinPcap, and Npcap is application/vnd.tcpdump.pcap. The typical file extension is .pcap, although .cap and .dmp are also in common use.[7]
History
libpcap was originally developed by the tcpdump developers in the Network Research Group at Lawrence Berkeley Laboratory. The low-level packet capture, capture file reading, and capture file writing code of tcpdump was extracted and made into a library, with which tcpdump was linked.[8] It is now developed by the same tcpdump.org group that develops tcpdump.[9]
pcap libraries for Windows
While libpcap was originally developed for Unix-like operating systems, a successful port for Windows was made, called WinPcap. It has been unmaintained since 2013,[10] and several competing forks have been released with new features and support for newer versions of Windows.
implementations of a lower-level library for the listed operating systems, to communicate with those drivers;
a port of libpcap that uses the API offered by the low-level library implementations.
Programmers at the Politecnico di Torino wrote the original code. As of 2008, CACE Technologies, a company set up by some of the WinPcap developers, developed and maintained the product. CACE was acquired by Riverbed Technology on October 21, 2010.[12]
Because WinPcap uses the older NDIS 5.x APIs, it does not work on some builds of Windows 10, which have deprecated or removed those APIs in favor of the newer NDIS 6.x APIs. It also forces some limitations such as being unable to capture 802.1Q VLAN tags in Ethernet headers.
The WinPcap project has ceased development and WinPcap and WinDump are no longer maintained. The last official WinPcap release was 4.1.3 released March 8, 2013.[13]
Npcap
Npcap is the Nmap Project's packet sniffing library for Windows.[14] It is based on WinPcap, but written to make use of Windows networking improvements in NDIS version 6. Its authors rewrote the WinPcap NDIS 5 Protocol Driver as a Light-Weight Filter (LWF) driver, a change that reduces processing overhead.[15]
Npcap maintenance releases updated the version of the included libpcap library to the latest available, allowing software authors to use the newer API features that Linux software had already supported.[16] Most software that used WinPcap can be easily ported to use Npcap with minimal changes.[17]
Npcap introduced several innovations that were not available in WinPcap:
Npcap can be restricted so that only Administrators can sniff packets.[18]
Npcap can capture 802.11 WiFi frames on a variety of commonly-available network adapters.[20]
Unlike Nmap, Npcap is proprietary software and requires a special license for use and redistribution except for some limited internal uses.[21]
Win10Pcap
Win10Pcap implementation is also based on the NDIS 6 driver model and works stably with Windows 10.[22] The project, however, has been inactive since 2016.[23]
Programs that use or used libpcap
Bit-Twist, a libpcap-based Ethernet packet generator and editor for BSD, Linux, and Windows.
Cain and Abel, a discontinued password recovery tool for Microsoft Windows
EtherApe, a graphical tool for monitoring network traffic and bandwidth usage in real time.
Suricata, a network intrusion prevention and analysis platform.
Symantec Data Loss Prevention, Used to monitor and identify sensitive data, track its use, and location. Data loss policies allow sensitive data to be blocked from leaving the network or copied to another device.
tcpdump, a tool for capturing and dumping packets for further analysis, and WinDump, the Windows port of tcpdump.
