NetSniffer 1.12.50.1 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The most frequent installer filenames for the software are: Manager.exe and netsniffer.exe etc.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The following versions: 1.1 and 1.0 are the most frequently downloaded ones by the program users. The actual developer of the free software is NetSniffer Software. NetSniffer lies within Internet & Network Tools, more precisely Network Tools.
From the developer:
NetSniffer is an interesting tool when setting up a home network, for instance to test if a certain PC really receives and transmits data. Additional, NetSniffer allows any user to inspect by himself, which data the attached PCs actually transmit. PCs, which send data over the LAN unwantedly, can so be easily retrieved. NetSniffer is able to intercept network packets already on the lowest level, the Ethernet layer.
You may want to check out more software, such as dotNet Sniffer Win32, which might be similar to NetSniffer.