A network analyzer (sniffer). It analyzes the data passing through your network.

SoftPerfect Network Protocol Analyzer is an advanced, professional tool for analyzing, debugging, maintaining and monitoring local networks and Internet connections. It captures the data passing through your dial-up connection or network Ethernet card, analyzes this data and then represents it in an easily readable form. SoftPerfect Network Protocol Analyzer is a useful tool for network administrators, security specialists, network application developers and anyone who needs a comprehensive picture of the traffic passing through their network connection or segment of a local area network. SoftPerfect Network Protocol Analyzer presents the results of its network analysis in a convenient and easily understandable format. It also allows you to defragment and reassemble network packets into streams. The program can easily analyze network traffic based on a number of different Internet protocols as listed below. SoftPerfect Network Protocol Analyzer features full decoding of the following low level protocols: AH, ARP, BOOTP, DHCP, DNS, ESP, GRE, ICMP, ICMPv6, IP, IPv6, IPX, LLC, MSG, REVARP, RIP, SAP, SER, SNAP, SPX, TCP, UDP and VLAN. It also performs full reconstruction of top-level protocols such as HTTP, SMTP, POP, IMAP, FTP, TELNET and others. The flexible system of fully configurable filters can be used to discard all network traffic except the specific traffic patterns you wish to analyze. SoftPerfect Network Protocol Analyzer also has a special packet builder. This tool allows you to build your own custom network packets and send them into the network. You could use this packet builder feature to check your network for protection against attacks and intruders. The software requires Windows 95/98/ME/NT/2000/XP. It also requires a network connection that could be a wireless connection or a modem that conforms to the NDIS standard.