Download net2pcap. Please audit ! Send remarks to and
Maybe PCAPdispatcher will help you to analyse your captures.


Net2PCAP is a simple network to pcap capture file for Linux. Its goal is to be as simple as possible (hence auditable) so that good confidence can be reached, for it to be used in hostile environments. It does not use any library except a bit of libc. It does not do anything except dumping network traffic from an interface to a pcap file. It is less than 400 lines of C. Please audit it !

Comparison with tcpdump

Yes, tcpdump -w capfile can do almost the same. But the goal of tcpdump is network debugging (thus, lot of options, packet disassembly, etc.). The goal of net2pcap is to capture traffic into a file in hostile environments (honeypots, internet, etc.) for future analysis.


$ ./net2pcap -h
Usage: net2pcap -i interface [-pdx] [-f capfile] [-t ethertype] [-s snaplen]
        -p : doesn't go promiscuous
        -d : daemon mode (background + uses syslog)
        -x : hexdumps every packet on output (if not daemon)
         snaplen   defaults to 1600
         capfile   defaults to net2pcap.cap
         ethertype defaults to ETH_P_ALL (sniff all)

Capture file rotation

If the capture file already exists, packets are appended. When SIG_HUP is delivered to net2pcap, it will close and reopen the file. Thus, you can rotate capture files without loosing any packet :
# net2pcap -i eth0 -f pcapfile -d
And every day (for a 1 day archive) :
# mv pcapfile pcapfile.0
# killall -HUP net2pcap