There is only one file type that uses the .PCAP extension:
Packet Capture Data
Data file created by Wireshark (formerly Ethereal), a free program used for network analysis; contains network packet data created during a live network capture; used for "packet sniffing" and analyzing data network characteristics; can be analyzed using software that includes the libpcap or WinPcap libraries.
Wireshark is available for Mac, Windows, and Linux platforms. Professors and students often use the software for studying data communications.
NOTE: Wireshark was renamed from Ethereal in May, 2006 due to trademark issues.
Updated: April 7, 2012