Packet Capture or PCAP (also known as libpcap) is an application programming interface (API) that captures live network packet data from OSI model Layers 2-7.
Unix-like systems implement pcap in the libpcap library; for Windows, there is a port of libpcap named WinPcap that is no longer supported or developed, and a port named Npcap for Windows 7 and later that is still supported.
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Monitoring software may use libpcap, WinPcap, or Npcap to capture network packets travelling 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 use an object-oriented wrapper.
Why do I need to use PCAP?
PCAP is a valuable resource for file analysis and to monitor your network traffic. Packet collection tools like Wireshark allow you to collect network traffic and translate it into a format that’s human-readable. There are many reasons why PCAP is used to monitor networks. Some of the most common include monitoring bandwidth usage, identifying rogue DHCP servers, detecting malware, DNS resolution, and incident response.
For network administrators and security researchers, packet file analysis is a good way to detect network intrusions and other suspicious activity. For example, if a source is sending the network lots of malicious traffic, you can identify that on the software agent and then take action to remediate the attack.
Network analyzers like Wireshark create .pcap files to collect and record packet data from a network. PCAP comes in a range of formats including Libpcap, WinPcap, and PCAPng.
These PCAP files can be used to view TCP/IP and UDP network packets. If you want to record network traffic then you need to create a .pcapfile. You can create a .pcapfile by using a network analyzer or packet sniffing tool like Wireshark or tcpdump.
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What are the versions of PCAP?
As mentioned above, there are many different types of PCAP files, including:
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Libpcap
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WinPcap
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PCAPng
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Npcap
Each version has its own use cases and different types of network monitoring tools support different forms of PCAP files. For instance, Libpcap is a portable open-source c/C++ library designed for Linux and Mac OS users. Libpcap enables administrators to capture and filter packets. Packet sniffing tools like tcpdump use the Libpcap format.
For Windows users, there is the WinPcap format. WinPcap is another portable packet capture library designed for Windows devices. WinpCap can also capture and filter packets collected from the network. Tools like Wireshark, Nmap, and Snort use WinPCap to monitor devices but the protocol itself has been discontinued.
Pcapng or .pcap Next Generation Capture File Format is a more advanced version of PCAP that comes default with Wireshark. Pcapng can capture and store data. The type of data pcapng collects includes extended timestamp precision, user comments, and capture statistics to provide the user with additional information.
Tools like Wireshark are using PCAPng files because it can record more information than PCAP. However, the problem with PCAPng is that it isn’t compatible with as many tools as PCAP.
Npcap is a portable packet sniffing library for Windows produced by Nmap, one of the most well-known packet sniffing vendors. The library is faster and more secure than WinpCap. Npcap has support for Windows 10 and loopback packet capture injection so you can send and sniff loopback packets. Npcap is also supported by Wireshark.
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Windows 10 version 2004 and later
Windows 10's built-in network packet sniffer Pktmon has been updated with real-time monitoring and PCAPNG capture file format support with recent release of Windows 10 2004. Since the October 2018 update, Microsoft has quietly included a built-in packet sniffer called Pktmon in Windows 10.
Windows 10's built-in network packet sniffer Pktmon has been updated with real-time monitoring and PCAPNG capture file format support with recent release of Windows 10 2004.
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