Top 6 Security tools:
Nessus, Ethereal, Snort, Netcat, TCPdump, Hping, DNSiff, GFI LANguard, Ettercap, Nikto, John the Ripper, OpenSSH, TripWire, Kismet, NetFilter,
IP Filter, pf, fport, SAINT, OpenPGP.
These tools works on Linux and Xp.If your system is protected by these softwares then it is...