Reader favorites: 10 great free network tools

Nessus

Nessus has been one of the staples of a networker's bag of free tools for years. With more than 20,000 vulnerability checks (plug-ins), Nessus is a powerhouse application no network or security administrator should be without.

Like Nmap, in the early days using Nessus with the command line was rather cumbersome and the output difficult to decipher. It also ran on Linux, so a Linux server was necessary for scanning. But this isn't your father's Nessus, as it installs and runs easily on Windows with a crisp GUI interface.

After installation, scanning can commence immediately or a regular download of updated scanning variables can be configured. There are two such plug-in feeds available: the Direct feed provides plug-ins as they become available and is available for a fee, while the Registered feed is free, but the plug-ins are available seven days after they are available for the Direct feed.

Updating your scans is important, and if you don't think that changes can occur in a short period of time, think again.

I went two weeks without updating my scan information and when I ran a new scan it found more than 7MB of new information I needed to download.

So don't think that the free subscription database isn't kept up to date.

If your network infrastructure permits such, Nessus can run on anyone's machine.

If you don't have the infrastructure to protect against scans, and if you have public access ports, beware; finding a vulnerability can be as easy as an intruder running Nessus on your net. The same advice applies here as for Nmap: run it before the hackers do.

PuTTY

It wasn't too long ago that managing network devices via Telnet was commonplace. Telnet, that venerable terminal emulation program, was the first main link between the old hard-wired terminals of the mainframe days and a distributed networked environment. Yet Telnet, in all its glory, has one major problem that makes it unsuitable to remote access today: it's unencrypted.

Enter PuTTY, a free SSH client for Windows platforms. It provides for encrypted command-line interface access to network equipment running an SSH server. For those older devices that will only respond to Telnet, there is a Telnet option as well.

PuTTY is a small program but big on options for secure access to your network equipment and servers running an SSH daemon.

As with many other terminal emulators, PuTTY allows for logging of sessions. You can save your session settings as well. Also available with the package is a secure FTP client for transferring files encrypted and an RSA and DSA key generation utility.

PuTTY is one of those rare small freeware packages with huge benefits. It should be the first tool on your networker's USB stick (everyone has one, right?) if you have a need for secure access to network equipment or secure file transfers, as you will use it often.