Simply put, a firewall/intrusion detection soft are tools designed to protect the security of a computer system, to prevent unauthorized access to or from a private network , be it a private network or an individual PC. They are almost one and the same, as a firewall stops unauthorized access by Internet users from accessing private networks connected to the Internet, while intrusion detection system warns about an attempt, logs it and asks you what you want to do about it. They can be both hardware and software, or a combination of both. Usually, all messages entering or leaving the computer system pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

There are several types of firewall techniques:

• Packet filter: Looks at each packetentering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
• Application gateway: Applies security mechanisms to specific applications, such as and Telnet servers. This is very effective, but can impose a performance degradation.
• Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
• Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

In practice, many firewalls use two or more of these techniques together.

There are also several products that can watch your connections and ports. Review of them bellow too.

BlackICE Defender from NetworkIce.com is an intrusion detection soft It is the current favorite in the Windoze world right now. It will block hacking atempts, and will filter all kinds of junk while you are online. It has several security levels: trusting(lowest), cautious, nervous, paranoid(highest). It is almost self installing it asks you every time a strange conenctiong is attempted and it keeps a log too! http://www.clariondeveloper.comhas the ClearIce freeware which will assist you in analyzing the data that BlackICE produces

In the end, extremly well done firewall product but hard to use because it stops and ask you if you want to allow ALL outgoing and incoming packetges, plus the documentatiion on it is spotty and not complete.

At Guard has been sold to Norton2000, but you can still find it floating around on the net. It has many advantiges, it stops cookies, ads, java, Java Scripts, Active X, ICMP pings, and it can be set up to ask you every time a connection is made to and from your PC. geocities.com/tom_rapid/page5.html contains AtGuard Message board archives,
here is mine AtGuard FAQ on how to set it up, including how to make rules, ets.

Conclusions: very effective product, has MANY MANY options to play and fiddle with.

Proxomitron(totally free), from https://members.tripod.com/Proxomitron. Very easy to install and use, it will stop cookies, Java, and won't let any info to slip out of your PC. It has a wide range of settings. I would suggest you read the a how to use Proxomitron FAQ by AnoniMouse. Conclusion: GET IT and get it NOW!

ZeroLabs has been getting lots of hyped press lately. It's free, yes, and it is supposed to watch which of your programs communicate with the outside world. Unfortunatly, its GUI interface is made with big bold icons, silly looking interface, and besides, lots of other softs already do the same thing. Conclusions: nothing special, get it if you MUST, but why bother, really?

Lockedown Conclusions the worse of the lot, boy, are you a sucker!