0trace

0trace is a traceroute tool designed to operate within an existing, open TCP connection. This capability allows it to bypass certain stateful packet filters that would typically block traditional traceroute probes. The tool is particularly useful in environments with strict firewall rules that inspect and drop unsolicited packets.

Use cases include network reconnaissance where standard traceroute tools fail due to firewall restrictions. By piggybacking on established TCP sessions, 0trace can map network paths without triggering filter alerts. It consists of multiple components including 0trace.sh, sendprobe, and usleep.

The package has a small installed size of 43 KB and depends on libc6 and tcpdump. It is pre-packaged for Kali Linux, enabling quick deployment for penetration testing and network diagnostics.

0trace leverages an existing TCP connection to send traceroute probes, avoiding detection by stateful firewalls. The primary script 0trace.sh takes an interface, target IP, and optional target port to initiate probes over the open session. sendprobe handles packet crafting with source IP, destination IP, source port, destination port, sequence, and acknowledgment numbers. usleep provides microsecond-precision delays for timing control during probe transmission.